# HG changeset patch
# User Bryan O'Sullivan <bos@serpentine.com>
# Date 1234945329 28800
# Node ID b90b024729f143baf5d5d2bd2205edbcbde3c6cb
# Parent  8631da51309bf1c4de7791ebe5e93d6a6e77eb87
WIP DocBook snapshot that all compiles. Mirabile dictu!

diff -r 8631da51309b -r b90b024729f1 .hgignore
--- a/.hgignore	Mon Feb 09 23:25:40 2009 -0800
+++ b/.hgignore	Wed Feb 18 00:22:09 2009 -0800
@@ -35,3 +35,4 @@
 .*.swp
 .\#*
 .run
+xsl/system-xsl
diff -r 8631da51309b -r b90b024729f1 en/00book.xml
--- a/en/00book.xml	Mon Feb 09 23:25:40 2009 -0800
+++ b/en/00book.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -9,7 +9,22 @@
 
 <!ENTITY ch01     SYSTEM "ch01-intro.xml">
 <!ENTITY ch02     SYSTEM "ch02-tour-basic.xml">
+<!ENTITY ch03     SYSTEM "ch03-tour-merge.xml">
+<!ENTITY ch04     SYSTEM "ch04-concepts.xml">
+<!ENTITY ch05     SYSTEM "ch05-daily.xml">
+<!ENTITY ch06     SYSTEM "ch06-collab.xml">
+<!ENTITY ch07     SYSTEM "ch07-filenames.xml">
+<!ENTITY ch08     SYSTEM "ch08-branch.xml">
+<!ENTITY ch09     SYSTEM "ch09-undo.xml">
+<!ENTITY ch10     SYSTEM "ch10-hook.xml">
+<!ENTITY ch11     SYSTEM "ch11-template.xml">
 <!ENTITY ch12     SYSTEM "ch12-mq.xml">
+<!ENTITY ch13     SYSTEM "ch13-mq-collab.xml">
+<!ENTITY ch14     SYSTEM "ch14-hgext.xml">
+<!ENTITY appA     SYSTEM "appA-cmdref.xml">
+<!ENTITY appB     SYSTEM "appB-mq-ref.xml">
+<!ENTITY appC     SYSTEM "appC-srcinstall.xml">
+<!ENTITY appD     SYSTEM "appD-license.xml">
 
 <!-- Include our standard shortcuts. -->
 
@@ -41,5 +56,20 @@
 
   &ch01;
   &ch02;
+  &ch03;
+  &ch04;
+  &ch05;
+  &ch06;
+  &ch07;
+  &ch08;
+  &ch09;
+  &ch10;
+  &ch11;
   &ch12;
+  &ch13;
+  &ch14;
+  <!-- &appA; -->
+  &appB;
+  &appC;
+  &appD;
 </book>
diff -r 8631da51309b -r b90b024729f1 en/Makefile
--- a/en/Makefile	Mon Feb 09 23:25:40 2009 -0800
+++ b/en/Makefile	Wed Feb 18 00:22:09 2009 -0800
@@ -33,9 +33,8 @@
 
 xml-src-files := \
 	00book.xml \
-	ch01-intro.xml \
-	ch02-tour-basic.xml \
-	ch12-mq.xml
+	app*.xml \
+	ch*.xml
 
 image-dot := $(filter %.dot,$(image-sources))
 image-svg := $(filter %.svg,$(image-sources))
diff -r 8631da51309b -r b90b024729f1 en/appA-cmdref.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/appA-cmdref.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,223 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<appendix id="cmdref">
+<title>Command reference</title>
+
+<para>\cmdref{add}{add files at the next commit}
+\optref{add}{I}{include}
+\optref{add}{X}{exclude}
+\optref{add}{n}{dry-run}</para>
+
+<para>\cmdref{diff}{print changes in history or working directory}</para>
+
+<para>Show differences between revisions for the specified files or
+directories, using the unified diff format.  For a description of the
+unified diff format, see section <xref linkend="sec:mq:patch"/>.</para>
+
+<para>By default, this command does not print diffs for files that Mercurial
+considers to contain binary data.  To control this behaviour, see the
+<option role="hg-opt-diff">-a</option> and <option role="hg-opt-diff">--git</option> options.</para>
+
+<sect2>
+<title>Options</title>
+
+<para>\loptref{diff}{nodates}</para>
+
+<para>Omit date and time information when printing diff headers.</para>
+
+<para>\optref{diff}{B}{ignore-blank-lines}</para>
+
+<para>Do not print changes that only insert or delete blank lines.  A line
+that contains only whitespace is not considered blank.
+</para>
+
+<para>\optref{diff}{I}{include}
+</para>
+
+<para>Include files and directories whose names match the given patterns.
+</para>
+
+<para>\optref{diff}{X}{exclude}
+</para>
+
+<para>Exclude files and directories whose names match the given patterns.
+</para>
+
+<para>\optref{diff}{a}{text}
+</para>
+
+<para>If this option is not specified, <command role="hg-cmd">hg diff</command> will refuse to print
+diffs for files that it detects as binary. Specifying <option role="hg-opt-diff">-a</option>
+forces <command role="hg-cmd">hg diff</command> to treat all files as text, and generate diffs for
+all of them.
+</para>
+
+<para>This option is useful for files that are <quote>mostly text</quote> but have a
+few embedded NUL characters.  If you use it on files that contain a
+lot of binary data, its output will be incomprehensible.
+</para>
+
+<para>\optref{diff}{b}{ignore-space-change}
+</para>
+
+<para>Do not print a line if the only change to that line is in the amount
+of white space it contains.
+</para>
+
+<para>\optref{diff}{g}{git}
+</para>
+
+<para>Print <command>git</command>-compatible diffs.  XXX reference a format
+description.
+</para>
+
+<para>\optref{diff}{p}{show-function}
+</para>
+
+<para>Display the name of the enclosing function in a hunk header, using a
+simple heuristic.  This functionality is enabled by default, so the
+<option role="hg-opt-diff">-p</option> option has no effect unless you change the value of
+the <envar role="rc-item-diff">showfunc</envar> config item, as in the following example.</para>
+
+<!-- &interaction.cmdref.diff-p; -->
+
+<para>\optref{diff}{r}{rev}
+</para>
+
+<para>Specify one or more revisions to compare.  The <command role="hg-cmd">hg diff</command> command
+accepts up to two <option role="hg-opt-diff">-r</option> options to specify the revisions to
+compare.
+</para>
+
+<orderedlist>
+<listitem><para>Display the differences between the parent revision of the
+  working directory and the working directory.
+</para>
+</listitem>
+<listitem><para>Display the differences between the specified changeset and the
+  working directory.
+</para>
+</listitem>
+<listitem><para>Display the differences between the two specified changesets.
+</para>
+</listitem></orderedlist>
+
+<para>You can specify two revisions using either two <option role="hg-opt-diff">-r</option>
+options or revision range notation.  For example, the two revision
+specifications below are equivalent.
+</para>
+<programlisting>hg diff -r 10 -r 20
+hg diff -r10:20</programlisting>
+
+<para>When you provide two revisions, Mercurial treats the order of those
+revisions as significant.  Thus, <command role="hg-cmd">hg diff -r10:20</command> will
+produce a diff that will transform files from their contents as of
+revision 10 to their contents as of revision 20, while
+<command role="hg-cmd">hg diff -r20:10</command> means the opposite: the diff that will
+transform files from their revision 20 contents to their revision 10
+contents.  You cannot reverse the ordering in this way if you are
+diffing against the working directory.
+</para>
+
+<para>\optref{diff}{w}{ignore-all-space}
+</para>
+
+<para>\cmdref{version}{print version and copyright information}
+</para>
+
+<para>This command displays the version of Mercurial you are running, and
+its copyright license.  There are four kinds of version string that
+you may see.
+</para>
+<itemizedlist>
+<listitem><para>The string <quote><literal>unknown</literal></quote>. This version of Mercurial was
+  not built in a Mercurial repository, and cannot determine its own
+  version.
+</para>
+</listitem>
+<listitem><para>A short numeric string, such as <quote><literal>1.1</literal></quote>. This is a
+  build of a revision of Mercurial that was identified by a specific
+  tag in the repository where it was built.  (This doesn't necessarily
+  mean that you're running an official release; someone else could
+  have added that tag to any revision in the repository where they
+  built Mercurial.)
+</para>
+</listitem>
+<listitem><para>A hexadecimal string, such as <quote><literal>875489e31abe</literal></quote>.  This
+  is a build of the given revision of Mercurial.
+</para>
+</listitem>
+<listitem><para>A hexadecimal string followed by a date, such as
+  <quote><literal>875489e31abe+20070205</literal></quote>.  This is a build of the given
+  revision of Mercurial, where the build repository contained some
+  local changes that had not been committed.
+</para>
+</listitem></itemizedlist>
+
+</sect2>
+<sect2>
+<title>Tips and tricks</title>
+
+<sect3 id="cmdref:diff-vs-status">
+<title>Why do the results of <command role="hg-cmd">hg diff</command> and <command role="hg-cmd">hg status</command> differ?</title>
+
+<para>When you run the <command role="hg-cmd">hg status</command> command, you'll see a list of files
+that Mercurial will record changes for the next time you perform a
+commit.  If you run the <command role="hg-cmd">hg diff</command> command, you may notice that it
+prints diffs for only a <emphasis>subset</emphasis> of the files that <command role="hg-cmd">hg status</command>
+listed.  There are two possible reasons for this.
+</para>
+
+<para>The first is that <command role="hg-cmd">hg status</command> prints some kinds of modifications
+that <command role="hg-cmd">hg diff</command> doesn't normally display.  The <command role="hg-cmd">hg diff</command> command
+normally outputs unified diffs, which don't have the ability to
+represent some changes that Mercurial can track.  Most notably,
+traditional diffs can't represent a change in whether or not a file is
+executable, but Mercurial records this information.
+</para>
+
+<para>If you use the <option role="hg-opt-diff">--git</option> option to <command role="hg-cmd">hg diff</command>, it will
+display <command>git</command>-compatible diffs that <emphasis>can</emphasis> display this
+extra information.
+</para>
+
+<para>The second possible reason that <command role="hg-cmd">hg diff</command> might be printing diffs
+for a subset of the files displayed by <command role="hg-cmd">hg status</command> is that if you
+invoke it without any arguments, <command role="hg-cmd">hg diff</command> prints diffs against the
+first parent of the working directory.  If you have run <command role="hg-cmd">hg merge</command>
+to merge two changesets, but you haven't yet committed the results of
+the merge, your working directory has two parents (use <command role="hg-cmd">hg parents</command>
+to see them).  While <command role="hg-cmd">hg status</command> prints modifications relative to
+<emphasis>both</emphasis> parents after an uncommitted merge, <command role="hg-cmd">hg diff</command> still
+operates relative only to the first parent.  You can get it to print
+diffs relative to the second parent by specifying that parent with the
+<option role="hg-opt-diff">-r</option> option.  There is no way to print diffs relative to
+both parents.
+</para>
+
+</sect3>
+<sect3>
+<title>Generating safe binary diffs</title>
+
+<para>If you use the <option role="hg-opt-diff">-a</option> option to force Mercurial to print
+diffs of files that are either <quote>mostly text</quote> or contain lots of
+binary data, those diffs cannot subsequently be applied by either
+Mercurial's <command role="hg-cmd">hg import</command> command or the system's <command>patch</command>
+command.
+</para>
+
+<para>If you want to generate a diff of a binary file that is safe to use as
+input for <command role="hg-cmd">hg import</command>, use the <command role="hg-cmd">hg diff</command>{--git} option when you
+generate the patch.  The system <command>patch</command> command cannot handle
+binary patches at all.
+</para>
+
+</sect3>
+</sect2>
+</appendix>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "appendix")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/appB-mq-ref.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/appB-mq-ref.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,568 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<appendix id="chap:mqref">
+  <title>Mercurial Queues reference</title>
+
+  <sect1 id="sec:mqref:cmdref">
+    <title>MQ command reference</title>
+
+    <para>For an overview of the commands provided by MQ, use the
+      command <command role="hg-cmd">hg help mq</command>.</para>
+
+    <sect2>
+      <title><command role="hg-ext-mq">qapplied</command>&emdash;print
+	applied patches</title>
+
+      <para>The <command role="hg-ext-mq">qapplied</command> command
+	prints the current stack of applied patches.  Patches are
+	printed in oldest-to-newest order, so the last patch in the
+	list is the <quote>top</quote> patch.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qcommit</command>&emdash;commit
+	changes in the queue repository</title>
+
+      <para>The <command role="hg-ext-mq">qcommit</command> command
+	commits any outstanding changes in the <filename
+	  role="special" class="directory">.hg/patches</filename>
+	repository.  This command only works if the <filename
+	  role="special" class="directory">.hg/patches</filename>
+	directory is a repository, i.e. you created the directory
+	using <command role="hg-cmd">hg qinit <option
+	    role="hg-ext-mq-cmd-qinit-opt">-c</option></command> or
+	ran <command role="hg-cmd">hg init</command> in the directory
+	after running <command
+	  role="hg-ext-mq">qinit</command>.</para>
+
+      <para>This command is shorthand for <command role="hg-cmd">hg
+	  commit --cwd .hg/patches</command>.</para>
+
+      <para>\subsection{<command
+	  role="hg-ext-mq">qdelete</command>&emdash;delete a patch
+	from the <filename role="special">series</filename>
+	file}</para>
+
+      <para>The <command role="hg-ext-mq">qdelete</command> command
+	removes the entry for a patch from the <filename
+	  role="special">series</filename> file in the <filename
+	  role="special" class="directory">.hg/patches</filename>
+	directory.  It does not pop the patch if the patch is already
+	applied.  By default, it does not delete the patch file; use
+	the <option role="hg-ext-mq-cmd-qdel-opt">-f</option> option
+	to do that.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qdel-opt">-f</option>: Delete the
+	    patch file.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qdiff</command>&emdash;print a
+	diff of the topmost applied patch</title>
+
+      <para>The <command role="hg-ext-mq">qdiff</command> command
+	prints a diff of the topmost applied patch. It is equivalent
+	to <command role="hg-cmd">hg diff -r-2:-1</command>.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qfold</command>&emdash;merge
+	(<quote>fold</quote>) several patches into one</title>
+
+      <para>The <command role="hg-ext-mq">qfold</command> command
+	merges multiple patches into the topmost applied patch, so
+	that the topmost applied patch makes the union of all of the
+	changes in the patches in question.</para>
+
+      <para>The patches to fold must not be applied; <command
+	  role="hg-ext-mq">qfold</command> will exit with an error if
+	any is.  The order in which patches are folded is significant;
+	<command role="hg-cmd">hg qfold a b</command> means
+	<quote>apply the current topmost patch, followed by
+	  <literal>a</literal>, followed by
+	  <literal>b</literal></quote>.</para>
+
+      <para>The comments from the folded patches are appended to the
+	comments of the destination patch, with each block of comments
+	separated by three asterisk
+	(<quote><literal>*</literal></quote>) characters.  Use the
+	<option role="hg-ext-mq-cmd-qfold-opt">-e</option> option to
+	edit the commit message for the combined patch/changeset after
+	the folding has completed.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qfold-opt">-e</option>: Edit the
+	    commit message and patch description for the newly folded
+	    patch.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qfold-opt">-l</option>: Use the
+	    contents of the given file as the new commit message and
+	    patch description for the folded patch.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qfold-opt">-m</option>: Use the
+	    given text as the new commit message and patch description
+	    for the folded patch.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title><command
+	  role="hg-ext-mq">qheader</command>&emdash;display the
+	header/description of a patch</title>
+
+      <para>The <command role="hg-ext-mq">qheader</command> command
+	prints the header, or description, of a patch.  By default, it
+	prints the header of the topmost applied patch. Given an
+	argument, it prints the header of the named patch.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qimport</command>&emdash;import
+	a third-party patch into the queue</title>
+
+      <para>The <command role="hg-ext-mq">qimport</command> command
+	adds an entry for an external patch to the <filename
+	  role="special">series</filename> file, and copies the patch
+	into the <filename role="special"
+	  class="directory">.hg/patches</filename> directory.  It adds
+	the entry immediately after the topmost applied patch, but
+	does not push the patch.</para>
+
+      <para>If the <filename role="special"
+	  class="directory">.hg/patches</filename> directory is a
+	repository, <command role="hg-ext-mq">qimport</command>
+	automatically does an <command role="hg-cmd">hg add</command>
+	of the imported patch.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qinit</command>&emdash;prepare
+	a repository to work with MQ</title>
+
+      <para>The <command role="hg-ext-mq">qinit</command> command
+	prepares a repository to work with MQ.  It creates a directory
+	called <filename role="special"
+	  class="directory">.hg/patches</filename>.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qinit-opt">-c</option>: Create
+	    <filename role="special"
+	      class="directory">.hg/patches</filename> as a repository
+	    in its own right.  Also creates a <filename
+	      role="special">.hgignore</filename> file that will
+	    ignore the <filename role="special">status</filename>
+	    file.</para>
+	</listitem></itemizedlist>
+
+      <para>When the <filename role="special"
+	  class="directory">.hg/patches</filename> directory is a
+	repository, the <command role="hg-ext-mq">qimport</command>
+	and <command role="hg-ext-mq">qnew</command> commands
+	automatically <command role="hg-cmd">hg add</command> new
+	patches.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qnew</command>&emdash;create a
+	new patch</title>
+
+      <para>The <command role="hg-ext-mq">qnew</command> command
+	creates a new patch.  It takes one mandatory argument, the
+	name to use for the patch file.  The newly created patch is
+	created empty by default.  It is added to the <filename
+	  role="special">series</filename> file after the current
+	topmost applied patch, and is immediately pushed on top of
+	that patch.</para>
+
+      <para>If <command role="hg-ext-mq">qnew</command> finds modified
+	files in the working directory, it will refuse to create a new
+	patch unless the <option
+	  role="hg-ext-mq-cmd-qnew-opt">-f</option> option is used
+	(see below).  This behaviour allows you to <command
+	  role="hg-ext-mq">qrefresh</command> your topmost applied
+	patch before you apply a new patch on top of it.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qnew-opt">-f</option>: Create a new
+	    patch if the contents of the working directory are
+	    modified.  Any outstanding modifications are added to the
+	    newly created patch, so after this command completes, the
+	    working directory will no longer be modified.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qnew-opt">-m</option>: Use the given
+	    text as the commit message. This text will be stored at
+	    the beginning of the patch file, before the patch
+	    data.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qnext</command>&emdash;print
+	the name of the next patch</title>
+
+      <para>The <command role="hg-ext-mq">qnext</command> command
+	prints the name name of the next patch in the <filename
+	  role="special">series</filename> file after the topmost
+	applied patch.  This patch will become the topmost applied
+	patch if you run <command
+	  role="hg-ext-mq">qpush</command>.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qpop</command>&emdash;pop
+	patches off the stack</title>
+
+      <para>The <command role="hg-ext-mq">qpop</command> command
+	removes applied patches from the top of the stack of applied
+	patches.  By default, it removes only one patch.</para>
+
+      <para>This command removes the changesets that represent the
+	popped patches from the repository, and updates the working
+	directory to undo the effects of the patches.</para>
+
+      <para>This command takes an optional argument, which it uses as
+	the name or index of the patch to pop to.  If given a name, it
+	will pop patches until the named patch is the topmost applied
+	patch.  If given a number, <command
+	  role="hg-ext-mq">qpop</command> treats the number as an
+	index into the entries in the series file, counting from zero
+	(empty lines and lines containing only comments do not count).
+	It pops patches until the patch identified by the given index
+	is the topmost applied patch.</para>
+
+      <para>The <command role="hg-ext-mq">qpop</command> command does
+	not read or write patches or the <filename
+	  role="special">series</filename> file.  It is thus safe to
+	<command role="hg-ext-mq">qpop</command> a patch that you have
+	removed from the <filename role="special">series</filename>
+	file, or a patch that you have renamed or deleted entirely.
+	In the latter two cases, use the name of the patch as it was
+	when you applied it.</para>
+
+      <para>By default, the <command role="hg-ext-mq">qpop</command>
+	command will not pop any patches if the working directory has
+	been modified.  You can override this behaviour using the
+	<option role="hg-ext-mq-cmd-qpop-opt">-f</option> option,
+	which reverts all modifications in the working
+	directory.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpop-opt">-a</option>: Pop all
+	    applied patches.  This returns the repository to its state
+	    before you applied any patches.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpop-opt">-f</option>: Forcibly
+	    revert any modifications to the working directory when
+	    popping.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpop-opt">-n</option>: Pop a patch
+	    from the named queue.</para>
+	</listitem></itemizedlist>
+
+      <para>The <command role="hg-ext-mq">qpop</command> command
+	removes one line from the end of the <filename
+	  role="special">status</filename> file for each patch that it
+	pops.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qprev</command>&emdash;print
+	the name of the previous patch</title>
+
+      <para>The <command role="hg-ext-mq">qprev</command> command
+	prints the name of the patch in the <filename
+	  role="special">series</filename> file that comes before the
+	topmost applied patch. This will become the topmost applied
+	patch if you run <command
+	  role="hg-ext-mq">qpop</command>.</para>
+
+    </sect2>
+    <sect2 id="sec:mqref:cmd:qpush">
+      <title><command role="hg-ext-mq">qpush</command>&emdash;push
+	patches onto the stack</title>
+
+      <para>The <command role="hg-ext-mq">qpush</command> command adds
+	patches onto the applied stack.  By default, it adds only one
+	patch.</para>
+
+      <para>This command creates a new changeset to represent each
+	applied patch, and updates the working directory to apply the
+	effects of the patches.</para>
+
+      <para>The default data used when creating a changeset are as
+	follows:</para>
+      <itemizedlist>
+	<listitem><para>The commit date and time zone are the current
+	    date and time zone.  Because these data are used to
+	    compute the identity of a changeset, this means that if
+	    you <command role="hg-ext-mq">qpop</command> a patch and
+	    <command role="hg-ext-mq">qpush</command> it again, the
+	    changeset that you push will have a different identity
+	    than the changeset you popped.</para>
+	</listitem>
+	<listitem><para>The author is the same as the default used by
+	    the <command role="hg-cmd">hg commit</command>
+	    command.</para>
+	</listitem>
+	<listitem><para>The commit message is any text from the patch
+	    file that comes before the first diff header.  If there is
+	    no such text, a default commit message is used that
+	    identifies the name of the patch.</para>
+	</listitem></itemizedlist>
+      <para>If a patch contains a Mercurial patch header (XXX add
+	link), the information in the patch header overrides these
+	defaults.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpush-opt">-a</option>: Push all
+	    unapplied patches from the <filename
+	      role="special">series</filename> file until there are
+	    none left to push.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpush-opt">-l</option>: Add the name
+	    of the patch to the end of the commit message.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpush-opt">-m</option>: If a patch
+	    fails to apply cleanly, use the entry for the patch in
+	    another saved queue to compute the parameters for a
+	    three-way merge, and perform a three-way merge using the
+	    normal Mercurial merge machinery.  Use the resolution of
+	    the merge as the new patch content.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qpush-opt">-n</option>: Use the
+	    named queue if merging while pushing.</para>
+	</listitem></itemizedlist>
+
+      <para>The <command role="hg-ext-mq">qpush</command> command
+	reads, but does not modify, the <filename
+	  role="special">series</filename> file.  It appends one line
+	to the <command role="hg-cmd">hg status</command> file for
+	each patch that it pushes.</para>
+
+    </sect2>
+    <sect2>
+      <title><command
+	  role="hg-ext-mq">qrefresh</command>&emdash;update the
+	topmost applied patch</title>
+
+      <para>The <command role="hg-ext-mq">qrefresh</command> command
+	updates the topmost applied patch.  It modifies the patch,
+	removes the old changeset that represented the patch, and
+	creates a new changeset to represent the modified
+	patch.</para>
+
+      <para>The <command role="hg-ext-mq">qrefresh</command> command
+	looks for the following modifications:</para>
+      <itemizedlist>
+	<listitem><para>Changes to the commit message, i.e. the text
+	    before the first diff header in the patch file, are
+	    reflected in the new changeset that represents the
+	    patch.</para>
+	</listitem>
+	<listitem><para>Modifications to tracked files in the working
+	    directory are added to the patch.</para>
+	</listitem>
+	<listitem><para>Changes to the files tracked using <command
+	      role="hg-cmd">hg add</command>, <command
+	      role="hg-cmd">hg copy</command>, <command
+	      role="hg-cmd">hg remove</command>, or <command
+	      role="hg-cmd">hg rename</command>.  Added files and copy
+	    and rename destinations are added to the patch, while
+	    removed files and rename sources are removed.</para>
+	</listitem></itemizedlist>
+
+      <para>Even if <command role="hg-ext-mq">qrefresh</command>
+	detects no changes, it still recreates the changeset that
+	represents the patch.  This causes the identity of the
+	changeset to differ from the previous changeset that
+	identified the patch.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qrefresh-opt">-e</option>: Modify
+	    the commit and patch description, using the preferred text
+	    editor.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qrefresh-opt">-m</option>: Modify
+	    the commit message and patch description, using the given
+	    text.</para>
+	</listitem>
+	<listitem><para><option
+	      role="hg-ext-mq-cmd-qrefresh-opt">-l</option>: Modify
+	    the commit message and patch description, using text from
+	    the given file.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qrename</command>&emdash;rename
+	a patch</title>
+
+      <para>The <command role="hg-ext-mq">qrename</command> command
+	renames a patch, and changes the entry for the patch in the
+	<filename role="special">series</filename> file.</para>
+
+      <para>With a single argument, <command
+	  role="hg-ext-mq">qrename</command> renames the topmost
+	applied patch.  With two arguments, it renames its first
+	argument to its second.</para>
+
+    </sect2>
+    <sect2>
+      <title><command
+	  role="hg-ext-mq">qrestore</command>&emdash;restore saved
+	queue state</title>
+
+      <para>XXX No idea what this does.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qsave</command>&emdash;save
+	current queue state</title>
+
+      <para>XXX Likewise.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qseries</command>&emdash;print
+	the entire patch series</title>
+
+      <para>The <command role="hg-ext-mq">qseries</command> command
+	prints the entire patch series from the <filename
+	  role="special">series</filename> file.  It prints only patch
+	names, not empty lines or comments.  It prints in order from
+	first to be applied to last.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-ext-mq">qtop</command>&emdash;print the
+	name of the current patch</title>
+
+      <para>The <command role="hg-ext-mq">qtop</command> prints the
+	name of the topmost currently applied patch.</para>
+
+    </sect2>
+    <sect2>
+      <title><command
+	  role="hg-ext-mq">qunapplied</command>&emdash;print patches
+	not yet applied</title>
+
+      <para>The <command role="hg-ext-mq">qunapplied</command> command
+	prints the names of patches from the <filename
+	  role="special">series</filename> file that are not yet
+	applied.  It prints them in order from the next patch that
+	will be pushed to the last.</para>
+
+    </sect2>
+    <sect2>
+      <title><command role="hg-cmd">hg strip</command>&emdash;remove a
+	revision and descendants</title>
+
+      <para>The <command role="hg-cmd">hg strip</command> command
+	removes a revision, and all of its descendants, from the
+	repository.  It undoes the effects of the removed revisions
+	from the repository, and updates the working directory to the
+	first parent of the removed revision.</para>
+
+      <para>The <command role="hg-cmd">hg strip</command> command
+	saves a backup of the removed changesets in a bundle, so that
+	they can be reapplied if removed in error.</para>
+
+      <para>Options:</para>
+      <itemizedlist>
+	<listitem><para><option role="hg-opt-strip">-b</option>: Save
+	    unrelated changesets that are intermixed with the stripped
+	    changesets in the backup bundle.</para>
+	</listitem>
+	<listitem><para><option role="hg-opt-strip">-f</option>: If a
+	    branch has multiple heads, remove all heads. XXX This
+	    should be renamed, and use <literal>-f</literal> to strip
+	    revs when there are pending changes.</para>
+	</listitem>
+	<listitem><para><option role="hg-opt-strip">-n</option>: Do
+	    not save a backup bundle.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>MQ file reference</title>
+
+    <sect2>
+      <title>The <filename role="special">series</filename>
+	file</title>
+
+      <para>The <filename role="special">series</filename> file
+	contains a list of the names of all patches that MQ can apply.
+	It is represented as a list of names, with one name saved per
+	line.  Leading and trailing white space in each line are
+	ignored.</para>
+
+      <para>Lines may contain comments.  A comment begins with the
+	<quote><literal>#</literal></quote> character, and extends to
+	the end of the line.  Empty lines, and lines that contain only
+	comments, are ignored.</para>
+
+      <para>You will often need to edit the <filename
+	  role="special">series</filename> file by hand, hence the
+	support for comments and empty lines noted above.  For
+	example, you can comment out a patch temporarily, and <command
+	  role="hg-ext-mq">qpush</command> will skip over that patch
+	when applying patches.  You can also change the order in which
+	patches are applied by reordering their entries in the
+	<filename role="special">series</filename> file.</para>
+
+      <para>Placing the <filename role="special">series</filename>
+	file under revision control is also supported; it is a good
+	idea to place all of the patches that it refers to under
+	revision control, as well.  If you create a patch directory
+	using the <option role="hg-ext-mq-cmd-qinit-opt">-c</option>
+	option to <command role="hg-ext-mq">qinit</command>, this will
+	be done for you automatically.</para>
+
+    </sect2>
+    <sect2>
+      <title>The <filename role="special">status</filename>
+	file</title>
+
+      <para>The <filename role="special">status</filename> file
+	contains the names and changeset hashes of all patches that MQ
+	currently has applied.  Unlike the <filename
+	  role="special">series</filename> file, this file is not
+	intended for editing.  You should not place this file under
+	revision control, or modify it in any way.  It is used by MQ
+	strictly for internal book-keeping.</para>
+
+    </sect2>
+  </sect1>
+</appendix>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "appendix")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/appC-srcinstall.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/appC-srcinstall.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,65 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<appendix id="chap:srcinstall">
+  <title>Installing Mercurial from source</title>
+
+  <sect1 id="sec:srcinstall:unixlike">
+    <title>On a Unix-like system</title>
+
+    <para>If you are using a Unix-like system that has a sufficiently
+      recent version of Python (2.3 or newer) available, it is easy to
+      install Mercurial from source.</para>
+    <orderedlist>
+      <listitem><para>Download a recent source tarball from <ulink
+	    url="http://www.selenic.com/mercurial/download">http://www.selenic.com/mercurial/download</ulink>.</para>
+      </listitem>
+      <listitem><para>Unpack the tarball:</para>
+	<programlisting>gzip -dc mercurial-MYVERSION.tar.gz | tar xf -</programlisting>
+      </listitem>
+      <listitem><para>Go into the source directory and run the
+	  installer script.  This will build Mercurial and install it
+	  in your home directory.</para>
+	<programlisting>cd mercurial-MYVERSION
+python setup.py install --force --home=$HOME</programlisting>
+      </listitem>
+    </orderedlist>
+    <para>Once the install finishes, Mercurial will be in the
+      <literal>bin</literal> subdirectory of your home directory.
+      Don't forget to make sure that this directory is present in your
+      shell's search path.</para>
+
+    <para>You will probably need to set the <envar>PYTHONPATH</envar>
+      environment variable so that the Mercurial executable can find
+      the rest of the Mercurial packages.  For example, on my laptop,
+      I have set it to <literal>/home/bos/lib/python</literal>.  The
+      exact path that you will need to use depends on how Python was
+      built for your system, but should be easy to figure out.  If
+      you're uncertain, look through the output of the installer
+      script above, and see where the contents of the
+      <literal>mercurial</literal> directory were installed to.</para>
+
+  </sect1>
+  <sect1>
+    <title>On Windows</title>
+
+    <para>Building and installing Mercurial on Windows requires a
+      variety of tools, a fair amount of technical knowledge, and
+      considerable patience.  I very much <emphasis>do not
+	recommend</emphasis> this route if you are a <quote>casual
+	user</quote>.  Unless you intend to hack on Mercurial, I
+      strongly suggest that you use a binary package instead.</para>
+
+    <para>If you are intent on building Mercurial from source on
+      Windows, follow the <quote>hard way</quote> directions on the
+      Mercurial wiki at <ulink
+	url="http://www.selenic.com/mercurial/wiki/index.cgi/WindowsInstall">http://www.selenic.com/mercurial/wiki/index.cgi/WindowsInstall</ulink>, 
+      and expect the process to involve a lot of fiddly work.</para>
+
+  </sect1>
+</appendix>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "appendix")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/appD-license.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/appD-license.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,178 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<appendix id="cha:opl">
+  <title>Open Publication License</title>
+
+  <para>Version 1.0, 8 June 1999</para>
+
+  <sect1>
+    <title>Requirements on both unmodified and modified
+      versions</title>
+
+    <para>The Open Publication works may be reproduced and distributed
+      in whole or in part, in any medium physical or electronic,
+      provided that the terms of this license are adhered to, and that
+      this license or an incorporation of it by reference (with any
+      options elected by the author(s) and/or publisher) is displayed
+      in the reproduction.</para>
+
+    <para>Proper form for an incorporation by reference is as
+      follows:</para>
+
+    <blockquote>
+      <para>  Copyright (c) <emphasis>year</emphasis> by
+	<emphasis>author's name or designee</emphasis>. This material
+	may be distributed only subject to the terms and conditions
+	set forth in the Open Publication License,
+	v<emphasis>x.y</emphasis> or later (the latest version is
+	presently available at <ulink
+	  url="http://www.opencontent.org/openpub/">http://www.opencontent.org/openpub/</ulink>).</para>
+    </blockquote>
+
+    <para>The reference must be immediately followed with any options
+      elected by the author(s) and/or publisher of the document (see
+      section <xref linkend="sec:opl:options"/>).</para>
+
+    <para>Commercial redistribution of Open Publication-licensed
+      material is permitted.</para>
+
+    <para>Any publication in standard (paper) book form shall require
+      the citation of the original publisher and author. The publisher
+      and author's names shall appear on all outer surfaces of the
+      book. On all outer surfaces of the book the original publisher's
+      name shall be as large as the title of the work and cited as
+      possessive with respect to the title.</para>
+
+  </sect1>
+  <sect1>
+    <title>Copyright</title>
+
+    <para>The copyright to each Open Publication is owned by its
+      author(s) or designee.</para>
+
+  </sect1>
+  <sect1>
+    <title>Scope of license</title>
+
+    <para>The following license terms apply to all Open Publication
+      works, unless otherwise explicitly stated in the
+      document.</para>
+
+    <para>Mere aggregation of Open Publication works or a portion of
+      an Open Publication work with other works or programs on the
+      same media shall not cause this license to apply to those other
+      works. The aggregate work shall contain a notice specifying the
+      inclusion of the Open Publication material and appropriate
+      copyright notice.</para>
+
+    <para><emphasis role="bold">Severability</emphasis>. If any part
+      of this license is found to be unenforceable in any
+      jurisdiction, the remaining portions of the license remain in
+      force.</para>
+
+    <para><emphasis role="bold">No warranty</emphasis>. Open
+      Publication works are licensed and provided <quote>as is</quote>
+      without warranty of any kind, express or implied, including, but
+      not limited to, the implied warranties of merchantability and
+      fitness for a particular purpose or a warranty of
+      non-infringement.</para>
+
+  </sect1>
+  <sect1>
+    <title>Requirements on modified works</title>
+
+    <para>All modified versions of documents covered by this license,
+      including translations, anthologies, compilations and partial
+      documents, must meet the following requirements:</para>
+
+    <orderedlist>
+      <listitem><para>The modified version must be labeled as
+	  such.</para>
+      </listitem>
+      <listitem><para>The person making the modifications must be
+	  identified and the modifications dated.</para>
+      </listitem>
+      <listitem><para>Acknowledgement of the original author and
+	  publisher if applicable must be retained according to normal
+	  academic citation practices.</para>
+      </listitem>
+      <listitem><para>The location of the original unmodified document
+	  must be identified.</para>
+      </listitem>
+      <listitem><para>The original author's (or authors') name(s) may
+	  not be used to assert or imply endorsement of the resulting
+	  document without the original author's (or authors')
+	  permission.</para>
+      </listitem></orderedlist>
+
+  </sect1>
+  <sect1>
+    <title>Good-practice recommendations</title>
+
+    <para>In addition to the requirements of this license, it is
+      requested from and strongly recommended of redistributors
+      that:</para>
+
+    <orderedlist>
+      <listitem><para>If you are distributing Open Publication works
+	  on hardcopy or CD-ROM, you provide email notification to the
+	  authors of your intent to redistribute at least thirty days
+	  before your manuscript or media freeze, to give the authors
+	  time to provide updated documents. This notification should
+	  describe modifications, if any, made to the document.</para>
+      </listitem>
+      <listitem><para>All substantive modifications (including
+	  deletions) be either clearly marked up in the document or
+	  else described in an attachment to the document.</para>
+      </listitem>
+      <listitem><para>Finally, while it is not mandatory under this
+	  license, it is considered good form to offer a free copy of
+	  any hardcopy and CD-ROM expression of an Open
+	  Publication-licensed work to its author(s).</para>
+      </listitem></orderedlist>
+
+  </sect1>
+  <sect1 id="sec:opl:options">
+    <title>License options</title>
+
+    <para>The author(s) and/or publisher of an Open
+      Publication-licensed document may elect certain options by
+      appending language to the reference to or copy of the license.
+      These options are considered part of the license instance and
+      must be included with the license (or its incorporation by
+      reference) in derived works.</para>
+
+    <orderedlist>
+      <listitem><para>To prohibit distribution of substantively
+	  modified versions without the explicit permission of the
+	  author(s). <quote>Substantive modification</quote> is
+	  defined as a change to the semantic content of the document,
+	  and excludes mere changes in format or typographical
+	  corrections.</para>
+      </listitem>
+      <listitem><para>  To accomplish this, add the phrase
+	  <quote>Distribution of substantively modified versions of
+	    this document is prohibited without the explicit
+	    permission of the copyright holder.</quote> to the license
+	  reference or copy.</para>
+      </listitem>
+      <listitem><para>To prohibit any publication of this work or
+	  derivative works in whole or in part in standard (paper)
+	  book form for commercial purposes is prohibited unless prior
+	  permission is obtained from the copyright holder.</para>
+      </listitem>
+      <listitem><para>To accomplish this, add the phrase
+	  <quote>Distribution of the work or derivative of the work in
+	    any standard (paper) book form is prohibited unless prior
+	    permission is obtained from the copyright holder.</quote>
+	  to the license reference or copy.</para>
+      </listitem></orderedlist>
+
+  </sect1>
+</appendix>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "appendix")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch00-preface.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch00-preface.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,80 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<preface id="chap:preface">
+  <title>Preface</title>
+
+  <para>Distributed revision control is a relatively new territory,
+    and has thus far grown due to people's willingness to strike out
+    into ill-charted territory.</para>
+
+  <para>I am writing a book about distributed revision control because
+    I believe that it is an important subject that deserves a field
+    guide. I chose to write about Mercurial because it is the easiest
+    tool to learn the terrain with, and yet it scales to the demands
+    of real, challenging environments where many other revision
+    control tools fail.</para>
+
+  <sect1>
+    <title>This book is a work in progress</title>
+
+    <para>I am releasing this book while I am still writing it, in the
+      hope that it will prove useful to others.  I also hope that
+      readers will contribute as they see fit.</para>
+
+  </sect1>
+  <sect1>
+    <title>About the examples in this book</title>
+
+    <para>This book takes an unusual approach to code samples.  Every
+      example is <quote>live</quote>---each one is actually the result
+      of a shell script that executes the Mercurial commands you see.
+      Every time an image of the book is built from its sources, all
+      the example scripts are automatically run, and their current
+      results compared against their expected results.</para>
+
+    <para>The advantage of this approach is that the examples are
+      always accurate; they describe <emphasis>exactly</emphasis> the
+      behaviour of the version of Mercurial that's mentioned at the
+      front of the book.  If I update the version of Mercurial that
+      I'm documenting, and the output of some command changes, the
+      build fails.</para>
+
+    <para>There is a small disadvantage to this approach, which is
+      that the dates and times you'll see in examples tend to be
+      <quote>squashed</quote> together in a way that they wouldn't be
+      if the same commands were being typed by a human.  Where a human
+      can issue no more than one command every few seconds, with any
+      resulting timestamps correspondingly spread out, my automated
+      example scripts run many commands in one second.</para>
+
+    <para>As an instance of this, several consecutive commits in an
+      example can show up as having occurred during the same second.
+      You can see this occur in the <literal
+	role="hg-ext">bisect</literal> example in section <xref
+	id="sec:undo:bisect"/>, for instance.</para>
+
+    <para>So when you're reading examples, don't place too much weight
+      on the dates or times you see in the output of commands.  But
+      <emphasis>do</emphasis> be confident that the behaviour you're
+      seeing is consistent and reproducible.</para>
+
+  </sect1>
+  <sect1>
+    <title>Colophon---this book is Free</title>
+
+    <para>This book is licensed under the Open Publication License,
+      and is produced entirely using Free Software tools.  It is
+      typeset with \LaTeX{}; illustrations are drawn and rendered with
+      <ulink url="http://www.inkscape.org/">Inkscape</ulink>.</para>
+
+    <para>The complete source code for this book is published as a
+      Mercurial repository, at <ulink
+	url="http://hg.serpentine.com/mercurial/book">http://hg.serpentine.com/mercurial/book</ulink>.</para>
+
+  </sect1>
+</preface>
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "preface")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch02-tour-basic.xml
--- a/en/ch02-tour-basic.xml	Mon Feb 09 23:25:40 2009 -0800
+++ b/en/ch02-tour-basic.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -1,12 +1,10 @@
 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
 
-<chapter>
+<chapter id="chap:tour-basic">
   <title>A tour of Mercurial: the basics</title>
-  <para>\label{chap:tour-basic}</para>
-
-  <sect1>
+
+  <sect1 id="sec:tour:install">
     <title>Installing Mercurial on your system</title>
-    <para>\label{sec:tour:install}</para>
 
     <para>Prebuilt binary packages of Mercurial are available for
       every popular operating system.  These make it easy to start
@@ -65,10 +63,10 @@
       <para>Lee Cantey publishes an installer of Mercurial for Mac OS
 	X at <ulink
 	  url="http://mercurial.berkwood.com">http://mercurial.berkwood.com</ulink>. 
-	This package works on both Intel- and Power-based Macs.
-	Before you can use it, you must install a compatible version
-	of Universal MacPython <citation>web:macpython</citation>.
-	This is easy to do; simply follow the instructions on Lee's
+	This package works on both Intel- and Power-based Macs. Before
+	you can use it, you must install a compatible version of
+	Universal MacPython <citation>web:macpython</citation>. This
+	is easy to do; simply follow the instructions on Lee's
 	site.</para>
 
       <para>It's also possible to install Mercurial using Fink or
@@ -104,26 +102,31 @@
 	version</command> command to find out whether Mercurial is
       actually installed properly.  The actual version information
       that it prints isn't so important; it's whether it prints
-      anything at all that we care about. <!--
-      &interaction.tour.version; --></para>
+      anything at all that we care about.</para>
+
+      <!-- &interaction.tour.version; -->
 
     <sect2>
       <title>Built-in help</title>
 
       <para>Mercurial provides a built-in help system.  This is
-	invaluable for those times when you find yourself stuck trying
-	to remember how to run a command.  If you are completely
-	stuck, simply run <command role="hg-cmd">hg help</command>; it
-	will print a brief list of commands, along with a description
-	of what each does.  If you ask for help on a specific command
-	(as below), it prints more detailed information. <!--
-	&interaction.tour.help; --> For a more impressive level of
-	detail (which you won't usually need) run <command
-	  role="hg-cmd">hg help <option
-	    role="hg-opt-global">-v</option></command>.  The <option
-	  role="hg-opt-global">-v</option> option is short for <option
-	  role="hg-opt-global">--verbose</option>, and tells Mercurial
-	to print more information than it usually would.</para>
+	  invaluable for those times when you find yourself stuck
+	  trying to remember how to run a command.  If you are
+	  completely stuck, simply run <command role="hg-cmd">hg
+	    help</command>; it will print a brief list of commands,
+	  along with a description of what each does.  If you ask for
+	  help on a specific command (as below), it prints more
+	  detailed information.</para>
+
+	<!-- &interaction.tour.help; -->
+
+	<para>For a more impressive level of detail (which you won't
+	  usually need) run <command role="hg-cmd">hg help <option
+	      role="hg-opt-global">-v</option></command>.  The <option
+	    role="hg-opt-global">-v</option> option is short for
+	  <option role="hg-opt-global">--verbose</option>, and tells
+	  Mercurial to print more information than it usually
+	  would.</para>
 
     </sect2>
   </sect1>
@@ -150,13 +153,18 @@
 	command to make a copy of a repository, it's best to use a
 	built-in command that Mercurial provides.  This command is
 	called <command role="hg-cmd">hg clone</command>, because it
-	creates an identical copy of an existing repository. <!--
-	&interaction.tour.clone; --> If our clone succeeded, we should
-	now have a local directory called <filename
-	  class="directory">hello</filename>.  This directory will
-	contain some files. <!-- &interaction.tour.ls; --> These files
-	have the same contents and history in our repository as they
-	do in the repository we cloned.</para>
+	creates an identical copy of an existing repository.</para>
+
+      <!-- &interaction.tour.clone; -->
+
+      <para>If our clone succeeded, we should now have a local
+	directory called <filename class="directory">hello</filename>.
+	This directory will contain some files.</para>
+
+      <!-- &interaction.tour.ls; -->
+
+      <para>These files have the same contents and history in our
+	repository as they do in the repository we cloned.</para>
 
       <para>Every Mercurial repository is complete, self-contained,
 	and independent.  It contains its own private copy of a
@@ -176,8 +184,9 @@
       <para>When we take a more detailed look inside a repository, we
 	can see that it contains a directory named <filename
 	  class="directory">.hg</filename>.  This is where Mercurial
-	keeps all of its metadata for the repository. <!--
-	&interaction.tour.ls-a; --></para>
+	keeps all of its metadata for the repository.</para>
+
+      <!-- &interaction.tour.ls-a; -->
 
       <para>The contents of the <filename
 	  class="directory">.hg</filename> directory and its
@@ -205,10 +214,13 @@
     <para>One of the first things we might want to do with a new,
       unfamiliar repository is understand its history.  The <command
 	role="hg-cmd">hg log</command> command gives us a view of
-      history. <!-- &interaction.tour.log; --> By default, this
-      command prints a brief paragraph of output for each change to
-      the project that was recorded.  In Mercurial terminology, we
-      call each of these recorded events a
+      history.</para>
+
+    <!-- &interaction.tour.log; -->
+
+    <para>By default, this command prints a brief paragraph of output
+      for each change to the project that was recorded.  In Mercurial
+      terminology, we call each of these recorded events a
       <emphasis>changeset</emphasis>, because it can contain a record
       of changes to several files.</para>
 
@@ -310,18 +322,22 @@
 	  role="hg-opt-log">-r</option> (or <option
 	  role="hg-opt-log">--rev</option>) option.  You can use
 	either a revision number or a long-form changeset identifier,
-	and you can provide as many revisions as you want.  <!--
-	&interaction.tour.log-r; --></para>
+	and you can provide as many revisions as you want.</para>
+
+      <!-- &interaction.tour.log-r; -->
 
       <para>If you want to see the history of several revisions
 	without having to list each one, you can use <emphasis>range
 	  notation</emphasis>; this lets you express the idea <quote>I
-	  want all revisions between $a$ and $b$, inclusive</quote>.
-	<!-- &interaction.tour.log.range; --> Mercurial also honours
-	the order in which you specify revisions, so <command
-	  role="hg-cmd">hg log -r 2:4</command> prints $2,3,4$ while
-	<command role="hg-cmd">hg log -r 4:2</command> prints
-	$4,3,2$.</para>
+	  want all revisions between <literal>abc</literal> and
+	  <literal>def</literal>, inclusive</quote>.</para>
+      
+	<!-- &interaction.tour.log.range; -->
+
+      <para>Mercurial also honours the order in which you specify
+	revisions, so <command role="hg-cmd">hg log -r 2:4</command>
+	prints 2, 3, and 4. while <command role="hg-cmd">hg log -r
+	  4:2</command> prints 4, 3, and 2.</para>
 
     </sect2>
     <sect2>
@@ -335,7 +351,9 @@
 	looking for. The <command role="hg-cmd">hg log</command>
 	command's <option role="hg-opt-global">-v</option> (or <option
 	  role="hg-opt-global">--verbose</option>) option gives you
-	this extra detail. <!-- &interaction.tour.log-v; --></para>
+	this extra detail.</para>
+
+      <!-- &interaction.tour.log-v; -->
 
       <para>If you want to see both the description and content of a
 	change, add the <option role="hg-opt-log">-p</option> (or
@@ -343,7 +361,9 @@
 	displays the content of a change as a <emphasis>unified
 	  diff</emphasis> (if you've never seen a unified diff before,
 	see section <xref linkend="sec:mq:patch"/> for an
-	overview). <!-- &interaction.tour.log-vp; --></para>
+	overview).</para>
+
+      <!-- &interaction.tour.log-vp; -->
 
     </sect2>
   </sect1>
@@ -402,16 +422,18 @@
       the remote repository.  Since we already have a copy of it
       locally, we can just clone that instead.  This is much faster
       than cloning over the network, and cloning a local repository
-      uses less disk space in most cases, too. <!--
-      &interaction.tour.reclone; --> As an aside, it's often good
-      practice to keep a <quote>pristine</quote> copy of a remote
-      repository around, which you can then make temporary clones of
-      to create sandboxes for each task you want to work on.  This
-      lets you work on multiple tasks in parallel, each isolated from
-      the others until it's complete and you're ready to integrate it
-      back.  Because local clones are so cheap, there's almost no
-      overhead to cloning and destroying repositories whenever you
-      want.</para>
+      uses less disk space in most cases, too.</para>
+
+    <!-- &interaction.tour.reclone; -->
+
+    <para>As an aside, it's often good practice to keep a
+      <quote>pristine</quote> copy of a remote repository around,
+      which you can then make temporary clones of to create sandboxes
+      for each task you want to work on.  This lets you work on
+      multiple tasks in parallel, each isolated from the others until
+      it's complete and you're ready to integrate it back.  Because
+      local clones are so cheap, there's almost no overhead to cloning
+      and destroying repositories whenever you want.</para>
 
     <para>In our <filename class="directory">my-hello</filename>
       repository, we have a file <filename>hello.c</filename> that
@@ -422,13 +444,18 @@
       to write a scripted example this way.  Since you're not under
       the same constraint, you probably won't want to use
       <command>sed</command>; simply use your preferred text editor to
-      do the same thing.) <!-- &interaction.tour.sed; --></para>
+      do the same thing.)</para>
+
+    <!-- &interaction.tour.sed; -->
 
     <para>Mercurial's <command role="hg-cmd">hg status</command>
       command will tell us what Mercurial knows about the files in the
-      repository. <!-- &interaction.tour.status; --> The <command
-	role="hg-cmd">hg status</command> command prints no output for
-      some files, but a line starting with
+      repository.</para>
+
+    <!-- &interaction.tour.status; -->
+
+    <para>The <command role="hg-cmd">hg status</command> command
+      prints no output for some files, but a line starting with
       <quote><literal>M</literal></quote> for
       <filename>hello.c</filename>.  Unless you tell it to, <command
 	role="hg-cmd">hg status</command> will not print any output
@@ -446,7 +473,9 @@
       <filename>hello.c</filename>, but we might prefer to know
       exactly <emphasis>what</emphasis> changes we've made to it.  To
       do this, we use the <command role="hg-cmd">hg diff</command>
-      command. <!-- &interaction.tour.diff; --></para>
+      command.</para>
+
+    <!-- &interaction.tour.diff; -->
 
   </sect1>
   <sect1>
@@ -701,67 +730,70 @@
     <sect2>
       <title>Updating the working directory</title>
 
-      <para>We have so far glossed over the relationship
-	  between a repository and its working directory.  The
-	  <command role="hg-cmd">hg pull</command> command that we ran
-	  in section <xref linkend="sec:tour:pull"/> brought changes into
-	  the
-	  repository, but if we check, there's no sign of those
-	  changes in the working directory.  This is because <command
-	    role="hg-cmd">hg pull</command> does not (by default)
-	  touch the working directory.  Instead, we use the <command
-	    role="hg-cmd">hg update</command> command to do this. <!--
-	  &interaction.tour.update; --></para>
-      <para>It might seem a bit strange that <command
-	    role="hg-cmd">hg pull</command> doesn't update the working
-	  directory automatically.  There's actually a good reason for
-	  this: you can use <command role="hg-cmd">hg update</command>
-	  to update the working directory to the state it was in at
-	  <emphasis>any revision</emphasis> in the history of the
-	  repository.  If you had the working directory updated to an
-	  old revision---to hunt down the origin of a bug, say---and
-	  ran a <command role="hg-cmd">hg pull</command> which
-	  automatically updated the working directory to a new
-	  revision, you might not be terribly happy.</para>
-      <para>However, since pull-then-update is such a common
-	  thing to do, Mercurial lets you combine the two by passing
-	  the <option role="hg-opt-pull">-u</option> option to
-	  <command role="hg-cmd">hg
-	    pull</command>.</para>
+      <para>We have so far glossed over the relationship between a
+	repository and its working directory.  The <command
+	  role="hg-cmd">hg pull</command> command that we ran in
+	section <xref linkend="sec:tour:pull"/> brought changes
+	into the repository, but if we check, there's no sign of those
+	changes in the working directory.  This is because <command
+	  role="hg-cmd">hg pull</command> does not (by default) touch
+	the working directory.  Instead, we use the <command
+	  role="hg-cmd">hg update</command> command to do this.</para>
+
+      <!-- &interaction.tour.update; -->
+
+      <para>It might seem a bit strange that <command role="hg-cmd">hg
+	  pull</command> doesn't update the working directory
+	automatically.  There's actually a good reason for this: you
+	can use <command role="hg-cmd">hg update</command> to update
+	the working directory to the state it was in at <emphasis>any
+	  revision</emphasis> in the history of the repository.  If
+	you had the working directory updated to an old revision---to
+	hunt down the origin of a bug, say---and ran a <command
+	  role="hg-cmd">hg pull</command> which automatically updated
+	the working directory to a new revision, you might not be
+	terribly happy.</para>
+      <para>However, since pull-then-update is such a common thing to
+	do, Mercurial lets you combine the two by passing the <option
+	  role="hg-opt-pull">-u</option> option to <command
+	  role="hg-cmd">hg pull</command>.</para>
 
       <para>If you look back at the output of <command
-	    role="hg-cmd">hg pull</command> in section <xref
+	  role="hg-cmd">hg pull</command> in section <xref
 	    linkend="sec:tour:pull"/> when we ran it without <option
-	    role="hg-opt-pull">-u</option>, you can see that it
-	  printed a helpful reminder that we'd have to take an
-	  explicit step to update the working
-	  directory:</para>
+	  role="hg-opt-pull">-u</option>, you can see that it printed
+	a helpful reminder that we'd have to take an explicit step to
+	update the working directory:</para>
 
       <!-- &interaction.xxx.fixme; -->
 
-      <para>To find out what revision the working directory
-	  is at, use the <command role="hg-cmd">hg parents</command>
-	  command.</para>
+      <para>To find out what revision the working directory is at, use
+	the <command role="hg-cmd">hg parents</command>
+	command.</para>
 
       <!-- &interaction.tour.parents; -->
 
-      <para>If you look
-	  back at figure <xref linkend="fig:tour-basic:history"/>, you'll
-	  see arrows connecting each changeset.  The node that the
-	  arrow leads <emphasis>from</emphasis> in each case is a
-	  parent, and the node that the arrow leads
-	  <emphasis>to</emphasis> is its child.  The working directory
-	  has a parent in just the same way; this is the changeset
-	  that the working directory currently
-	  contains.</para>
-      <para>To update the working directory to a particular
-	  revision, give a revision number or changeset ID to the
-	  <command role="hg-cmd">hg update</command> command. <!--
-	  &interaction.tour.older; --> If you omit an explicit
-	  revision, <command role="hg-cmd">hg update</command> will
-	  update to the tip revision, as shown by the second call to
-	  <command role="hg-cmd">hg update</command> in the example
-	  above.</para>
+      <para>If you look back at figure <xref
+	  linkend="fig:tour-basic:history"/>,
+	you'll see arrows connecting each changeset.  The node that
+	the arrow leads <emphasis>from</emphasis> in each case is a
+	parent, and the node that the arrow leads
+	<emphasis>to</emphasis> is its child.  The working directory
+	has a parent in just the same way; this is the changeset that
+	the working directory currently contains.</para>
+
+      <para>To update the working directory to a particular revision,
+
+	give a revision number or changeset ID to the <command
+	  role="hg-cmd">hg update</command> command.</para>
+
+      <!-- &interaction.tour.older; -->
+
+      <para>If you omit an explicit revision, <command
+	  role="hg-cmd">hg update</command> will update to the tip
+	revision, as shown by the second call to <command
+	  role="hg-cmd">hg update</command> in the example
+	above.</para>
     </sect2>
 
     <sect2>
diff -r 8631da51309b -r b90b024729f1 en/ch03-tour-merge.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch03-tour-merge.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,394 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:tour-merge">
+  <title>A tour of Mercurial: merging work</title>
+
+  <para>We've now covered cloning a repository, making changes in a
+    repository, and pulling or pushing changes from one repository
+    into another.  Our next step is <emphasis>merging</emphasis>
+    changes from separate repositories.</para>
+
+  <sect1>
+    <title>Merging streams of work</title>
+
+    <para>Merging is a fundamental part of working with a distributed
+      revision control tool.</para>
+    <itemizedlist>
+      <listitem><para>Alice and Bob each have a personal copy of a
+	  repository for a project they're collaborating on.  Alice
+	  fixes a bug in her repository; Bob adds a new feature in
+	  his.  They want the shared repository to contain both the
+	  bug fix and the new feature.</para>
+      </listitem>
+      <listitem><para>I frequently work on several different tasks for
+	  a single project at once, each safely isolated in its own
+	  repository. Working this way means that I often need to
+	  merge one piece of my own work with another.</para>
+      </listitem></itemizedlist>
+
+    <para>Because merging is such a common thing to need to do,
+      Mercurial makes it easy.  Let's walk through the process.  We'll
+      begin by cloning yet another repository (see how often they
+      spring up?) and making a change in it.</para>
+
+    <!-- &interaction.tour.merge.clone; -->
+
+    <para>We should now have two copies of
+      <filename>hello.c</filename> with different contents.  The
+      histories of the two repositories have also diverged, as
+      illustrated in figure <xref
+	linkend="fig:tour-merge:sep-repos"/>.</para>
+
+    <!-- &interaction.tour.merge.cat; -->
+
+    <informalfigure id="fig:tour-merge:sep-repos">
+      <mediaobject>
+	<imageobject><imagedata fileref="tour-merge-sep-repos"/></imageobject>
+	<textobject><phrase>XXX add text</phrase></textobject>
+	<caption><para>Divergent recent histories of the <filename
+	      class="directory">my-hello</filename> and <filename
+	      class="directory">my-new-hello</filename>
+	    repositories</para></caption>
+      </mediaobject>
+    </informalfigure>
+
+    <para>We already know that pulling changes from our <filename
+	class="directory">my-hello</filename> repository will have no
+      effect on the working directory.</para>
+
+    <!-- &interaction.tour.merge.pull; -->
+
+    <para>However, the <command role="hg-cmd">hg pull</command>
+      command says something about <quote>heads</quote>.</para>
+
+    <sect2>
+      <title>Head changesets</title>
+
+      <para>A head is a change that has no descendants, or children,
+	as they're also known.  The tip revision is thus a head,
+	because the newest revision in a repository doesn't have any
+	children, but a repository can contain more than one
+	head.</para>
+
+      <informalfigure id="fig:tour-merge:pull">
+	<mediaobject><imageobject><imagedata
+				    fileref="tour-merge-pull"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject>
+	  <caption><para>Repository contents after pulling from
+	      <filename class="directory">my-hello</filename> into
+	      <filename
+		class="directory">my-new-hello</filename></para></caption>
+	</mediaobject>
+      </informalfigure>
+
+      <para>In figure <xref linkend="fig:tour-merge:pull"/>, you can
+	see the effect of the pull from <filename
+	  class="directory">my-hello</filename> into <filename
+	  class="directory">my-new-hello</filename>.  The history that
+	was already present in <filename
+	  class="directory">my-new-hello</filename> is untouched, but
+	a new revision has been added.  By referring to figure <xref
+	  linkend="fig:tour-merge:sep-repos"/>, we can see that the
+	<emphasis>changeset ID</emphasis> remains the same in the new
+	repository, but the <emphasis>revision number</emphasis> has
+	changed.  (This, incidentally, is a fine example of why it's
+	not safe to use revision numbers when discussing changesets.)
+	We can view the heads in a repository using the <command
+	  role="hg-cmd">hg heads</command> command.</para>
+
+      <!-- &interaction.tour.merge.heads; -->
+
+    </sect2>
+    <sect2>
+      <title>Performing the merge</title>
+
+      <para>What happens if we try to use the normal <command
+	  role="hg-cmd">hg update</command> command to update to the
+	new tip?</para>
+
+      <!-- &interaction.tour.merge.update; -->
+
+      <para>Mercurial is telling us that the <command role="hg-cmd">hg
+	  update</command> command won't do a merge; it won't update
+	the working directory when it thinks we might be wanting to do
+	a merge, unless we force it to do so.  Instead, we use the
+	<command role="hg-cmd">hg merge</command> command to merge the
+	two heads.</para>
+
+      <!-- &interaction.tour.merge.merge; -->
+
+      <informalfigure id="fig:tour-merge:merge">
+
+	<mediaobject><imageobject><imagedata
+				    fileref="tour-merge-merge"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject>
+	  <caption><para>Working directory and repository during
+	      merge, and following commit</para></caption>
+	</mediaobject>
+      </informalfigure>
+
+      <para>This updates the working directory so that it contains
+	changes from <emphasis>both</emphasis> heads, which is
+	reflected in both the output of <command role="hg-cmd">hg
+	  parents</command> and the contents of
+	<filename>hello.c</filename>.</para>
+
+      <!-- &interaction.tour.merge.parents; -->
+
+    </sect2>
+    <sect2>
+      <title>Committing the results of the merge</title>
+
+      <para>Whenever we've done a merge, <command role="hg-cmd">hg
+	  parents</command> will display two parents until we <command
+	  role="hg-cmd">hg commit</command> the results of the
+	  merge.</para>
+
+	<!-- &interaction.tour.merge.commit; -->
+
+      <para>We now have a new tip revision; notice that it has
+	<emphasis>both</emphasis> of our former heads as its parents.
+	These are the same revisions that were previously displayed by
+	<command role="hg-cmd">hg parents</command>.</para>
+
+      <!-- &interaction.tour.merge.tip; -->
+
+      <para>In figure <xref
+	  linkend="fig:tour-merge:merge"/>, you can see a
+	representation of what happens to the working directory during
+	the merge, and how this affects the repository when the commit
+	happens.  During the merge, the working directory has two
+	parent changesets, and these become the parents of the new
+	changeset.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Merging conflicting changes</title>
+
+    <para>Most merges are simple affairs, but sometimes you'll find
+      yourself merging changes where each modifies the same portions
+      of the same files.  Unless both modifications are identical,
+      this results in a <emphasis>conflict</emphasis>, where you have
+      to decide how to reconcile the different changes into something
+      coherent.</para>
+
+    <informalfigure>
+
+      <mediaobject id="fig:tour-merge:conflict">
+	<imageobject><imagedata fileref="tour-merge-conflict"/></imageobject>
+	<textobject><phrase>XXX add text</phrase></textobject>
+	<caption><para>Conflicting changes to a
+	    document</para></caption>      </mediaobject>
+    </informalfigure>
+
+    <para>Figure <xref linkend="fig:tour-merge:conflict"/> illustrates
+      an instance of two conflicting changes to a document.  We
+      started with a single version of the file; then we made some
+      changes; while someone else made different changes to the same
+      text.  Our task in resolving the conflicting changes is to
+      decide what the file should look like.</para>
+
+    <para>Mercurial doesn't have a built-in facility for handling
+      conflicts. Instead, it runs an external program called
+      <command>hgmerge</command>.  This is a shell script that is
+      bundled with Mercurial; you can change it to behave however you
+      please.  What it does by default is try to find one of several
+      different merging tools that are likely to be installed on your
+      system.  It first tries a few fully automatic merging tools; if
+      these don't succeed (because the resolution process requires
+      human guidance) or aren't present, the script tries a few
+      different graphical merging tools.</para>
+
+    <para>It's also possible to get Mercurial to run another program
+      or script instead of <command>hgmerge</command>, by setting the
+      <envar>HGMERGE</envar> environment variable to the name of your
+      preferred program.</para>
+
+    <sect2>
+      <title>Using a graphical merge tool</title>
+
+      <para>My preferred graphical merge tool is
+	<command>kdiff3</command>, which I'll use to describe the
+	features that are common to graphical file merging tools.  You
+	can see a screenshot of <command>kdiff3</command> in action in
+	figure <xref linkend="fig:tour-merge:kdiff3"/>.  The kind of
+	merge it is performing is called a <emphasis>three-way
+	  merge</emphasis>, because there are three different versions
+	of the file of interest to us.  The tool thus splits the upper
+	portion of the window into three panes:</para>
+      <itemizedlist>
+	<listitem><para>At the left is the <emphasis>base</emphasis>
+	    version of the file, i.e. the most recent version from
+	    which the two versions we're trying to merge are
+	    descended.</para>
+	</listitem>
+	<listitem><para>In the middle is <quote>our</quote> version of
+	    the file, with the contents that we modified.</para>
+	</listitem>
+	<listitem><para>On the right is <quote>their</quote> version
+	    of the file, the one that from the changeset that we're
+	    trying to merge with.</para>
+	</listitem></itemizedlist>
+      <para>In the pane below these is the current
+	<emphasis>result</emphasis> of the merge. Our task is to
+	replace all of the red text, which indicates unresolved
+	conflicts, with some sensible merger of the
+	<quote>ours</quote> and <quote>theirs</quote> versions of the
+	file.</para>
+
+      <para>All four of these panes are <emphasis>locked
+	  together</emphasis>; if we scroll vertically or horizontally
+	in any of them, the others are updated to display the
+	corresponding sections of their respective files.</para>
+
+      <informalfigure id="fig:tour-merge:kdiff3">
+	<mediaobject><imageobject><imagedata
+				    fileref="kdiff3"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject>
+	  <caption><para>Using <command>kdiff3</command> to merge
+	      versions of a file</para></caption>
+	</mediaobject>
+      </informalfigure>
+
+      <para>For each conflicting portion of the file, we can choose to
+	resolve the conflict using some combination of text from the
+	base version, ours, or theirs.  We can also manually edit the
+	merged file at any time, in case we need to make further
+	modifications.</para>
+
+      <para>There are <emphasis>many</emphasis> file merging tools
+	available, too many to cover here.  They vary in which
+	platforms they are available for, and in their particular
+	strengths and weaknesses.  Most are tuned for merging files
+	containing plain text, while a few are aimed at specialised
+	file formats (generally XML).</para>
+
+    </sect2>
+    <sect2>
+      <title>A worked example</title>
+
+      <para>In this example, we will reproduce the file modification
+	history of figure <xref linkend="fig:tour-merge:conflict"/>
+	above.  Let's begin by creating a repository with a base
+	version of our document.</para>
+
+      <!-- &interaction.tour-merge-conflict.wife; -->
+
+      <para>We'll clone the repository and make a change to the
+	file.</para>
+
+      <!-- &interaction.tour-merge-conflict.cousin; -->
+
+      <para>And another clone, to simulate someone else making a
+	change to the file. (This hints at the idea that it's not all
+	that unusual to merge with yourself when you isolate tasks in
+	separate repositories, and indeed to find and resolve
+	conflicts while doing so.)</para>
+
+      <!-- &interaction.tour-merge-conflict.son; -->
+
+      <para>Having created two
+	different versions of the file, we'll set up an environment
+	suitable for running our merge.</para>
+
+      <!-- &interaction.tour-merge-conflict.pull; -->
+
+      <para>In this example, I won't use Mercurial's normal
+	<command>hgmerge</command> program to do the merge, because it
+	would drop my nice automated example-running tool into a
+	graphical user interface.  Instead, I'll set
+	<envar>HGMERGE</envar> to tell Mercurial to use the
+	non-interactive <command>merge</command> command.  This is
+	bundled with many Unix-like systems. If you're following this
+	example on your computer, don't bother setting
+	<envar>HGMERGE</envar>.</para>
+
+      <para><emphasis role="bold">XXX FIX THIS
+	  EXAMPLE.</emphasis></para>
+
+      <!-- &interaction.tour-merge-conflict.merge; -->
+
+      <para>Because <command>merge</command> can't resolve the
+	conflicting changes, it leaves <emphasis>merge
+	  markers</emphasis> inside the file that has conflicts,
+	indicating which lines have conflicts, and whether they came
+	from our version of the file or theirs.</para>
+
+      <para>Mercurial can tell from the way <command>merge</command>
+	exits that it wasn't able to merge successfully, so it tells
+	us what commands we'll need to run if we want to redo the
+	merging operation.  This could be useful if, for example, we
+	were running a graphical merge tool and quit because we were
+	confused or realised we had made a mistake.</para>
+
+      <para>If automatic or manual merges fail, there's nothing to
+	prevent us from <quote>fixing up</quote> the affected files
+	ourselves, and committing the results of our merge:</para>
+
+      <!-- &interaction.tour-merge-conflict.commit; -->
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:tour-merge:fetch">
+    <title>Simplifying the pull-merge-commit sequence</title>
+
+    <para>The process of merging changes as outlined above is
+      straightforward, but requires running three commands in
+      sequence.</para>
+    <programlisting>
+      hg pull hg merge hg commit -m 'Merged remote changes'
+    </programlisting>
+    <para>In the case of the final commit, you also need to enter a
+      commit message, which is almost always going to be a piece of
+      uninteresting <quote>boilerplate</quote> text.</para>
+
+    <para>It would be nice to reduce the number of steps needed, if
+      this were possible.  Indeed, Mercurial is distributed with an
+      extension called <literal role="hg-ext">fetch</literal> that
+      does just this.</para>
+
+    <para>Mercurial provides a flexible extension mechanism that lets
+      people extend its functionality, while keeping the core of
+      Mercurial small and easy to deal with.  Some extensions add new
+      commands that you can use from the command line, while others
+      work <quote>behind the scenes,</quote> for example adding
+      capabilities to the server.</para>
+
+    <para>The <literal role="hg-ext">fetch</literal> extension adds a
+      new command called, not surprisingly, <command role="hg-cmd">hg
+	fetch</command>.  This extension acts as a combination of
+      <command role="hg-cmd">hg pull</command>, <command
+	role="hg-cmd">hg update</command> and <command
+	role="hg-cmd">hg merge</command>.  It begins by pulling
+      changes from another repository into the current repository.  If
+      it finds that the changes added a new head to the repository, it
+      begins a merge, then commits the result of the merge with an
+      automatically-generated commit message.  If no new heads were
+      added, it updates the working directory to the new tip
+      changeset.</para>
+
+    <para>Enabling the <literal role="hg-ext">fetch</literal>
+      extension is easy.  Edit your <filename
+	role="special">.hgrc</filename>, and either go to the <literal
+	role="rc-extensions">extensions</literal> section or create an
+      <literal role="rc-extensions">extensions</literal> section. Then
+      add a line that simply reads <quote><literal>fetch
+	</literal></quote>.</para>
+    <programlisting>
+      [extensions] fetch =
+    </programlisting>
+    <para>(Normally, on the right-hand side of the
+      <quote><literal>=</literal></quote> would appear the location of
+      the extension, but since the <literal
+	role="hg-ext">fetch</literal> extension is in the standard
+      distribution, Mercurial knows where to search for it.)</para>
+
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch04-concepts.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch04-concepts.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,725 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:concepts">
+  <title>Behind the scenes</title>
+
+  <para>Unlike many revision control systems, the concepts upon which
+    Mercurial is built are simple enough that it's easy to understand
+    how the software really works.  Knowing this certainly isn't
+    necessary, but I find it useful to have a <quote>mental
+      model</quote> of what's going on.</para>
+
+  <para>This understanding gives me confidence that Mercurial has been
+    carefully designed to be both <emphasis>safe</emphasis> and
+    <emphasis>efficient</emphasis>.  And just as importantly, if it's
+    easy for me to retain a good idea of what the software is doing
+    when I perform a revision control task, I'm less likely to be
+    surprised by its behaviour.</para>
+
+  <para>In this chapter, we'll initially cover the core concepts
+    behind Mercurial's design, then continue to discuss some of the
+    interesting details of its implementation.</para>
+
+  <sect1>
+    <title>Mercurial's historical record</title>
+
+    <sect2>
+      <title>Tracking the history of a single file</title>
+
+      <para>When Mercurial tracks modifications to a file, it stores
+	the history of that file in a metadata object called a
+	<emphasis>filelog</emphasis>.  Each entry in the filelog
+	contains enough information to reconstruct one revision of the
+	file that is being tracked.  Filelogs are stored as files in
+	the <filename role="special"
+	  class="directory">.hg/store/data</filename> directory.  A
+	filelog contains two kinds of information: revision data, and
+	an index to help Mercurial to find a revision
+	efficiently.</para>
+
+      <para>A file that is large, or has a lot of history, has its
+	filelog stored in separate data
+	(<quote><literal>.d</literal></quote> suffix) and index
+	(<quote><literal>.i</literal></quote> suffix) files.  For
+	small files without much history, the revision data and index
+	are combined in a single <quote><literal>.i</literal></quote>
+	file.  The correspondence between a file in the working
+	directory and the filelog that tracks its history in the
+	repository is illustrated in figure <xref
+	  linkend="fig:concepts:filelog"/>.</para>
+
+      <informalfigure id="fig:concepts:filelog">
+	<mediaobject><imageobject><imagedata
+				    fileref="filelog"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject>
+	  <caption><para>Relationships between files in working
+	      directory and filelogs in
+	      repository</para></caption></mediaobject>
+      </informalfigure>
+
+    </sect2>
+    <sect2>
+      <title>Managing tracked files</title>
+
+      <para>Mercurial uses a structure called a
+	<emphasis>manifest</emphasis> to collect together information
+	about the files that it tracks.  Each entry in the manifest
+	contains information about the files present in a single
+	changeset.  An entry records which files are present in the
+	changeset, the revision of each file, and a few other pieces
+	of file metadata.</para>
+
+    </sect2>
+    <sect2>
+      <title>Recording changeset information</title>
+
+      <para>The <emphasis>changelog</emphasis> contains information
+	about each changeset.  Each revision records who committed a
+	change, the changeset comment, other pieces of
+	changeset-related information, and the revision of the
+	manifest to use.</para>
+
+    </sect2>
+    <sect2>
+      <title>Relationships between revisions</title>
+
+      <para>Within a changelog, a manifest, or a filelog, each
+	revision stores a pointer to its immediate parent (or to its
+	two parents, if it's a merge revision).  As I mentioned above,
+	there are also relationships between revisions
+	<emphasis>across</emphasis> these structures, and they are
+	hierarchical in nature.</para>
+
+      <para>For every changeset in a repository, there is exactly one
+	revision stored in the changelog.  Each revision of the
+	changelog contains a pointer to a single revision of the
+	manifest.  A revision of the manifest stores a pointer to a
+	single revision of each filelog tracked when that changeset
+	was created.  These relationships are illustrated in figure
+	<xref linkend="fig:concepts:metadata"/>.</para>
+
+      <informalfigure id="fig:concepts:metadata">
+	<mediaobject><imageobject><imagedata
+				    fileref="metadata"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Metadata
+	      relationships</para></caption>
+	</mediaobject>
+      </informalfigure>
+
+      <para>As the illustration shows, there is
+	<emphasis>not</emphasis> a <quote>one to one</quote>
+	relationship between revisions in the changelog, manifest, or
+	filelog. If the manifest hasn't changed between two
+	changesets, the changelog entries for those changesets will
+	point to the same revision of the manifest.  If a file that
+	Mercurial tracks hasn't changed between two changesets, the
+	entry for that file in the two revisions of the manifest will
+	point to the same revision of its filelog.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Safe, efficient storage</title>
+
+    <para>The underpinnings of changelogs, manifests, and filelogs are
+      provided by a single structure called the
+      <emphasis>revlog</emphasis>.</para>
+
+    <sect2>
+      <title>Efficient storage</title>
+
+      <para>The revlog provides efficient storage of revisions using a
+	<emphasis>delta</emphasis> mechanism.  Instead of storing a
+	complete copy of a file for each revision, it stores the
+	changes needed to transform an older revision into the new
+	revision.  For many kinds of file data, these deltas are
+	typically a fraction of a percent of the size of a full copy
+	of a file.</para>
+
+      <para>Some obsolete revision control systems can only work with
+	deltas of text files.  They must either store binary files as
+	complete snapshots or encoded into a text representation, both
+	of which are wasteful approaches.  Mercurial can efficiently
+	handle deltas of files with arbitrary binary contents; it
+	doesn't need to treat text as special.</para>
+
+    </sect2>
+    <sect2 id="sec:concepts:txn">
+      <title>Safe operation</title>
+
+      <para>Mercurial only ever <emphasis>appends</emphasis> data to
+	the end of a revlog file. It never modifies a section of a
+	file after it has written it.  This is both more robust and
+	efficient than schemes that need to modify or rewrite
+	data.</para>
+
+      <para>In addition, Mercurial treats every write as part of a
+	<emphasis>transaction</emphasis> that can span a number of
+	files.  A transaction is <emphasis>atomic</emphasis>: either
+	the entire transaction succeeds and its effects are all
+	visible to readers in one go, or the whole thing is undone.
+	This guarantee of atomicity means that if you're running two
+	copies of Mercurial, where one is reading data and one is
+	writing it, the reader will never see a partially written
+	result that might confuse it.</para>
+
+      <para>The fact that Mercurial only appends to files makes it
+	easier to provide this transactional guarantee.  The easier it
+	is to do stuff like this, the more confident you should be
+	that it's done correctly.</para>
+
+    </sect2>
+    <sect2>
+      <title>Fast retrieval</title>
+
+      <para>Mercurial cleverly avoids a pitfall common to all earlier
+	revision control systems: the problem of <emphasis>inefficient
+	  retrieval</emphasis>. Most revision control systems store
+	the contents of a revision as an incremental series of
+	modifications against a <quote>snapshot</quote>.  To
+	reconstruct a specific revision, you must first read the
+	snapshot, and then every one of the revisions between the
+	snapshot and your target revision.  The more history that a
+	file accumulates, the more revisions you must read, hence the
+	longer it takes to reconstruct a particular revision.</para>
+
+      <informalfigure id="fig:concepts:snapshot">
+	<mediaobject><imageobject><imagedata
+				    fileref="snapshot"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Snapshot of
+	      a revlog, with incremental
+	      deltas</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>The innovation that Mercurial applies to this problem is
+	simple but effective.  Once the cumulative amount of delta
+	information stored since the last snapshot exceeds a fixed
+	threshold, it stores a new snapshot (compressed, of course),
+	instead of another delta.  This makes it possible to
+	reconstruct <emphasis>any</emphasis> revision of a file
+	quickly.  This approach works so well that it has since been
+	copied by several other revision control systems.</para>
+
+      <para>Figure <xref linkend="fig:concepts:snapshot"/> illustrates
+	the idea.  In an entry in a revlog's index file, Mercurial
+	stores the range of entries from the data file that it must
+	read to reconstruct a particular revision.</para>
+
+      <sect3>
+	<title>Aside: the influence of video compression</title>
+
+	<para>If you're familiar with video compression or have ever
+	  watched a TV feed through a digital cable or satellite
+	  service, you may know that most video compression schemes
+	  store each frame of video as a delta against its predecessor
+	  frame.  In addition, these schemes use <quote>lossy</quote>
+	  compression techniques to increase the compression ratio, so
+	  visual errors accumulate over the course of a number of
+	  inter-frame deltas.</para>
+
+	<para>Because it's possible for a video stream to <quote>drop
+	    out</quote> occasionally due to signal glitches, and to
+	  limit the accumulation of artefacts introduced by the lossy
+	  compression process, video encoders periodically insert a
+	  complete frame (called a <quote>key frame</quote>) into the
+	  video stream; the next delta is generated against that
+	  frame.  This means that if the video signal gets
+	  interrupted, it will resume once the next key frame is
+	  received.  Also, the accumulation of encoding errors
+	  restarts anew with each key frame.</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Identification and strong integrity</title>
+
+      <para>Along with delta or snapshot information, a revlog entry
+	contains a cryptographic hash of the data that it represents.
+	This makes it difficult to forge the contents of a revision,
+	and easy to detect accidental corruption.</para>
+
+      <para>Hashes provide more than a mere check against corruption;
+	they are used as the identifiers for revisions.  The changeset
+	identification hashes that you see as an end user are from
+	revisions of the changelog.  Although filelogs and the
+	manifest also use hashes, Mercurial only uses these behind the
+	scenes.</para>
+
+      <para>Mercurial verifies that hashes are correct when it
+	retrieves file revisions and when it pulls changes from
+	another repository.  If it encounters an integrity problem, it
+	will complain and stop whatever it's doing.</para>
+
+      <para>In addition to the effect it has on retrieval efficiency,
+	Mercurial's use of periodic snapshots makes it more robust
+	against partial data corruption.  If a revlog becomes partly
+	corrupted due to a hardware error or system bug, it's often
+	possible to reconstruct some or most revisions from the
+	uncorrupted sections of the revlog, both before and after the
+	corrupted section.  This would not be possible with a
+	delta-only storage model.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Revision history, branching, and merging</title>
+
+    <para>Every entry in a Mercurial revlog knows the identity of its
+      immediate ancestor revision, usually referred to as its
+      <emphasis>parent</emphasis>.  In fact, a revision contains room
+      for not one parent, but two.  Mercurial uses a special hash,
+      called the <quote>null ID</quote>, to represent the idea
+      <quote>there is no parent here</quote>.  This hash is simply a
+      string of zeroes.</para>
+
+    <para>In figure <xref linkend="fig:concepts:revlog"/>, you can see
+      an example of the conceptual structure of a revlog.  Filelogs,
+      manifests, and changelogs all have this same structure; they
+      differ only in the kind of data stored in each delta or
+      snapshot.</para>
+
+    <para>The first revision in a revlog (at the bottom of the image)
+      has the null ID in both of its parent slots.  For a
+      <quote>normal</quote> revision, its first parent slot contains
+      the ID of its parent revision, and its second contains the null
+      ID, indicating that the revision has only one real parent.  Any
+      two revisions that have the same parent ID are branches.  A
+      revision that represents a merge between branches has two normal
+      revision IDs in its parent slots.</para>
+
+    <informalfigure id="fig:concepts:revlog">
+      <mediaobject><imageobject><imagedata
+				  fileref="revlog"/></imageobject><textobject><phrase>XXX 
+	    add text</phrase></textobject></mediaobject>
+    </informalfigure>
+
+  </sect1>
+  <sect1>
+    <title>The working directory</title>
+
+    <para>In the working directory, Mercurial stores a snapshot of the
+      files from the repository as of a particular changeset.</para>
+
+    <para>The working directory <quote>knows</quote> which changeset
+      it contains.  When you update the working directory to contain a
+      particular changeset, Mercurial looks up the appropriate
+      revision of the manifest to find out which files it was tracking
+      at the time that changeset was committed, and which revision of
+      each file was then current.  It then recreates a copy of each of
+      those files, with the same contents it had when the changeset
+      was committed.</para>
+
+    <para>The <emphasis>dirstate</emphasis> contains Mercurial's
+      knowledge of the working directory.  This details which
+      changeset the working directory is updated to, and all of the
+      files that Mercurial is tracking in the working
+      directory.</para>
+
+    <para>Just as a revision of a revlog has room for two parents, so
+      that it can represent either a normal revision (with one parent)
+      or a merge of two earlier revisions, the dirstate has slots for
+      two parents.  When you use the <command role="hg-cmd">hg
+	update</command> command, the changeset that you update to is
+      stored in the <quote>first parent</quote> slot, and the null ID
+      in the second. When you <command role="hg-cmd">hg
+	merge</command> with another changeset, the first parent
+      remains unchanged, and the second parent is filled in with the
+      changeset you're merging with.  The <command role="hg-cmd">hg
+	parents</command> command tells you what the parents of the
+      dirstate are.</para>
+
+    <sect2>
+      <title>What happens when you commit</title>
+
+      <para>The dirstate stores parent information for more than just
+	book-keeping purposes.  Mercurial uses the parents of the
+	dirstate as <emphasis>the parents of a new
+	  changeset</emphasis> when you perform a commit.</para>
+
+      <informalfigure id="fig:concepts:wdir">
+	<mediaobject><imageobject><imagedata
+				    fileref="wdir"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>The working
+	      directory can have two
+	      parents</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>Figure <xref linkend="fig:concepts:wdir"/> shows the
+	normal state of the working directory, where it has a single
+	changeset as parent.  That changeset is the
+	<emphasis>tip</emphasis>, the newest changeset in the
+	repository that has no children.</para>
+
+      <informalfigure id="fig:concepts:wdir-after-commit">
+	<mediaobject><imageobject><imagedata
+				    fileref="wdir-after-commit"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>The working
+	      directory gains new parents after a
+	      commit</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>It's useful to think of the working directory as
+	<quote>the changeset I'm about to commit</quote>.  Any files
+	that you tell Mercurial that you've added, removed, renamed,
+	or copied will be reflected in that changeset, as will
+	modifications to any files that Mercurial is already tracking;
+	the new changeset will have the parents of the working
+	directory as its parents.</para>
+
+      <para>After a commit, Mercurial will update the parents of the
+	working directory, so that the first parent is the ID of the
+	new changeset, and the second is the null ID.  This is shown
+	in figure <xref linkend="fig:concepts:wdir-after-commit"/>.
+	Mercurial
+	doesn't touch any of the files in the working directory when
+	you commit; it just modifies the dirstate to note its new
+	parents.</para>
+
+    </sect2>
+    <sect2>
+      <title>Creating a new head</title>
+
+      <para>It's perfectly normal to update the working directory to a
+	changeset other than the current tip.  For example, you might
+	want to know what your project looked like last Tuesday, or
+	you could be looking through changesets to see which one
+	introduced a bug.  In cases like this, the natural thing to do
+	is update the working directory to the changeset you're
+	interested in, and then examine the files in the working
+	directory directly to see their contents as they were when you
+	committed that changeset.  The effect of this is shown in
+	figure <xref linkend="fig:concepts:wdir-pre-branch"/>.</para>
+
+      <informalfigure id="fig:concepts:wdir-pre-branch">
+	<mediaobject><imageobject><imagedata
+				    fileref="wdir-pre-branch"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>The working
+	      directory, updated to an older
+	      changeset</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>Having updated the working directory to an older
+	changeset, what happens if you make some changes, and then
+	commit?  Mercurial behaves in the same way as I outlined
+	above.  The parents of the working directory become the
+	parents of the new changeset.  This new changeset has no
+	children, so it becomes the new tip.  And the repository now
+	contains two changesets that have no children; we call these
+	<emphasis>heads</emphasis>.  You can see the structure that
+	this creates in figure <xref
+	  linkend="fig:concepts:wdir-branch"/>.</para>
+
+      <informalfigure id="fig:concepts:wdir-branch">
+	<mediaobject><imageobject><imagedata
+				    fileref="wdir-branch"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>After a
+	      commit made while synced to an older
+	      changeset</para></caption></mediaobject>
+      </informalfigure>
+
+      <note>
+	<para>  If you're new to Mercurial, you should keep in mind a
+	  common <quote>error</quote>, which is to use the <command
+	    role="hg-cmd">hg pull</command> command without any
+	  options.  By default, the <command role="hg-cmd">hg
+	    pull</command> command <emphasis>does not</emphasis>
+	  update the working directory, so you'll bring new changesets
+	  into your repository, but the working directory will stay
+	  synced at the same changeset as before the pull.  If you
+	  make some changes and commit afterwards, you'll thus create
+	  a new head, because your working directory isn't synced to
+	  whatever the current tip is.</para>
+
+	<para>  I put the word <quote>error</quote> in quotes because
+	  all that you need to do to rectify this situation is
+	  <command role="hg-cmd">hg merge</command>, then <command
+	    role="hg-cmd">hg commit</command>.  In other words, this
+	  almost never has negative consequences; it just surprises
+	  people.  I'll discuss other ways to avoid this behaviour,
+	  and why Mercurial behaves in this initially surprising way,
+	  later on.</para>
+      </note>
+
+    </sect2>
+    <sect2>
+      <title>Merging heads</title>
+
+      <para>When you run the <command role="hg-cmd">hg merge</command>
+	command, Mercurial leaves the first parent of the working
+	directory unchanged, and sets the second parent to the
+	changeset you're merging with, as shown in figure <xref
+	  linkend="fig:concepts:wdir-merge"/>.</para>
+
+      <informalfigure id="fig:concepts:wdir-merge">
+	<mediaobject><imageobject><imagedata
+				    fileref="wdir-merge"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Merging two
+	      heads</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>Mercurial also has to modify the working directory, to
+	merge the files managed in the two changesets.  Simplified a
+	little, the merging process goes like this, for every file in
+	the manifests of both changesets.</para>
+      <itemizedlist>
+	<listitem><para>If neither changeset has modified a file, do
+	    nothing with that file.</para>
+	</listitem>
+	<listitem><para>If one changeset has modified a file, and the
+	    other hasn't, create the modified copy of the file in the
+	    working directory.</para>
+	</listitem>
+	<listitem><para>If one changeset has removed a file, and the
+	    other hasn't (or has also deleted it), delete the file
+	    from the working directory.</para>
+	</listitem>
+	<listitem><para>If one changeset has removed a file, but the
+	    other has modified the file, ask the user what to do: keep
+	    the modified file, or remove it?</para>
+	</listitem>
+	<listitem><para>If both changesets have modified a file,
+	    invoke an external merge program to choose the new
+	    contents for the merged file.  This may require input from
+	    the user.</para>
+	</listitem>
+	<listitem><para>If one changeset has modified a file, and the
+	    other has renamed or copied the file, make sure that the
+	    changes follow the new name of the file.</para>
+	</listitem></itemizedlist>
+      <para>There are more details&emdash;merging has plenty of corner
+	cases&emdash;but these are the most common choices that are
+	involved in a merge.  As you can see, most cases are
+	completely automatic, and indeed most merges finish
+	automatically, without requiring your input to resolve any
+	conflicts.</para>
+
+      <para>When you're thinking about what happens when you commit
+	after a merge, once again the working directory is <quote>the
+	  changeset I'm about to commit</quote>.  After the <command
+	  role="hg-cmd">hg merge</command> command completes, the
+	working directory has two parents; these will become the
+	parents of the new changeset.</para>
+
+      <para>Mercurial lets you perform multiple merges, but you must
+	commit the results of each individual merge as you go.  This
+	is necessary because Mercurial only tracks two parents for
+	both revisions and the working directory.  While it would be
+	technically possible to merge multiple changesets at once, the
+	prospect of user confusion and making a terrible mess of a
+	merge immediately becomes overwhelming.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Other interesting design features</title>
+
+    <para>In the sections above, I've tried to highlight some of the
+      most important aspects of Mercurial's design, to illustrate that
+      it pays careful attention to reliability and performance.
+      However, the attention to detail doesn't stop there.  There are
+      a number of other aspects of Mercurial's construction that I
+      personally find interesting.  I'll detail a few of them here,
+      separate from the <quote>big ticket</quote> items above, so that
+      if you're interested, you can gain a better idea of the amount
+      of thinking that goes into a well-designed system.</para>
+
+    <sect2>
+      <title>Clever compression</title>
+
+      <para>When appropriate, Mercurial will store both snapshots and
+	deltas in compressed form.  It does this by always
+	<emphasis>trying to</emphasis> compress a snapshot or delta,
+	but only storing the compressed version if it's smaller than
+	the uncompressed version.</para>
+
+      <para>This means that Mercurial does <quote>the right
+	  thing</quote> when storing a file whose native form is
+	compressed, such as a <literal>zip</literal> archive or a JPEG
+	image.  When these types of files are compressed a second
+	time, the resulting file is usually bigger than the
+	once-compressed form, and so Mercurial will store the plain
+	<literal>zip</literal> or JPEG.</para>
+
+      <para>Deltas between revisions of a compressed file are usually
+	larger than snapshots of the file, and Mercurial again does
+	<quote>the right thing</quote> in these cases.  It finds that
+	such a delta exceeds the threshold at which it should store a
+	complete snapshot of the file, so it stores the snapshot,
+	again saving space compared to a naive delta-only
+	approach.</para>
+
+      <sect3>
+	<title>Network recompression</title>
+
+	<para>When storing revisions on disk, Mercurial uses the
+	  <quote>deflate</quote> compression algorithm (the same one
+	  used by the popular <literal>zip</literal> archive format),
+	  which balances good speed with a respectable compression
+	  ratio.  However, when transmitting revision data over a
+	  network connection, Mercurial uncompresses the compressed
+	  revision data.</para>
+
+	<para>If the connection is over HTTP, Mercurial recompresses
+	  the entire stream of data using a compression algorithm that
+	  gives a better compression ratio (the Burrows-Wheeler
+	  algorithm from the widely used <literal>bzip2</literal>
+	  compression package).  This combination of algorithm and
+	  compression of the entire stream (instead of a revision at a
+	  time) substantially reduces the number of bytes to be
+	  transferred, yielding better network performance over almost
+	  all kinds of network.</para>
+
+	<para>(If the connection is over <command>ssh</command>,
+	  Mercurial <emphasis>doesn't</emphasis> recompress the
+	  stream, because <command>ssh</command> can already do this
+	  itself.)</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Read/write ordering and atomicity</title>
+
+      <para>Appending to files isn't the whole story when it comes to
+	guaranteeing that a reader won't see a partial write.  If you
+	recall figure <xref linkend="fig:concepts:metadata"/>,
+	revisions in the
+	changelog point to revisions in the manifest, and revisions in
+	the manifest point to revisions in filelogs.  This hierarchy
+	is deliberate.</para>
+
+      <para>A writer starts a transaction by writing filelog and
+	manifest data, and doesn't write any changelog data until
+	those are finished.  A reader starts by reading changelog
+	data, then manifest data, followed by filelog data.</para>
+
+      <para>Since the writer has always finished writing filelog and
+	manifest data before it writes to the changelog, a reader will
+	never read a pointer to a partially written manifest revision
+	from the changelog, and it will never read a pointer to a
+	partially written filelog revision from the manifest.</para>
+
+    </sect2>
+    <sect2>
+      <title>Concurrent access</title>
+
+      <para>The read/write ordering and atomicity guarantees mean that
+	Mercurial never needs to <emphasis>lock</emphasis> a
+	repository when it's reading data, even if the repository is
+	being written to while the read is occurring. This has a big
+	effect on scalability; you can have an arbitrary number of
+	Mercurial processes safely reading data from a repository
+	safely all at once, no matter whether it's being written to or
+	not.</para>
+
+      <para>The lockless nature of reading means that if you're
+	sharing a repository on a multi-user system, you don't need to
+	grant other local users permission to
+	<emphasis>write</emphasis> to your repository in order for
+	them to be able to clone it or pull changes from it; they only
+	need <emphasis>read</emphasis> permission.  (This is
+	<emphasis>not</emphasis> a common feature among revision
+	control systems, so don't take it for granted!  Most require
+	readers to be able to lock a repository to access it safely,
+	and this requires write permission on at least one directory,
+	which of course makes for all kinds of nasty and annoying
+	security and administrative problems.)</para>
+
+      <para>Mercurial uses locks to ensure that only one process can
+	write to a repository at a time (the locking mechanism is safe
+	even over filesystems that are notoriously hostile to locking,
+	such as NFS).  If a repository is locked, a writer will wait
+	for a while to retry if the repository becomes unlocked, but
+	if the repository remains locked for too long, the process
+	attempting to write will time out after a while. This means
+	that your daily automated scripts won't get stuck forever and
+	pile up if a system crashes unnoticed, for example.  (Yes, the
+	timeout is configurable, from zero to infinity.)</para>
+
+      <sect3>
+	<title>Safe dirstate access</title>
+
+	<para>As with revision data, Mercurial doesn't take a lock to
+	  read the dirstate file; it does acquire a lock to write it.
+	  To avoid the possibility of reading a partially written copy
+	  of the dirstate file, Mercurial writes to a file with a
+	  unique name in the same directory as the dirstate file, then
+	  renames the temporary file atomically to
+	  <filename>dirstate</filename>.  The file named
+	  <filename>dirstate</filename> is thus guaranteed to be
+	  complete, not partially written.</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Avoiding seeks</title>
+
+      <para>Critical to Mercurial's performance is the avoidance of
+	seeks of the disk head, since any seek is far more expensive
+	than even a comparatively large read operation.</para>
+
+      <para>This is why, for example, the dirstate is stored in a
+	single file.  If there were a dirstate file per directory that
+	Mercurial tracked, the disk would seek once per directory.
+	Instead, Mercurial reads the entire single dirstate file in
+	one step.</para>
+
+      <para>Mercurial also uses a <quote>copy on write</quote> scheme
+	when cloning a repository on local storage.  Instead of
+	copying every revlog file from the old repository into the new
+	repository, it makes a <quote>hard link</quote>, which is a
+	shorthand way to say <quote>these two names point to the same
+	  file</quote>.  When Mercurial is about to write to one of a
+	revlog's files, it checks to see if the number of names
+	pointing at the file is greater than one.  If it is, more than
+	one repository is using the file, so Mercurial makes a new
+	copy of the file that is private to this repository.</para>
+
+      <para>A few revision control developers have pointed out that
+	this idea of making a complete private copy of a file is not
+	very efficient in its use of storage.  While this is true,
+	storage is cheap, and this method gives the highest
+	performance while deferring most book-keeping to the operating
+	system.  An alternative scheme would most likely reduce
+	performance and increase the complexity of the software, each
+	of which is much more important to the <quote>feel</quote> of
+	day-to-day use.</para>
+
+    </sect2>
+    <sect2>
+      <title>Other contents of the dirstate</title>
+
+      <para>Because Mercurial doesn't force you to tell it when you're
+	modifying a file, it uses the dirstate to store some extra
+	information so it can determine efficiently whether you have
+	modified a file.  For each file in the working directory, it
+	stores the time that it last modified the file itself, and the
+	size of the file at that time.</para>
+
+      <para>When you explicitly <command role="hg-cmd">hg
+	  add</command>, <command role="hg-cmd">hg remove</command>,
+	<command role="hg-cmd">hg rename</command> or <command
+	  role="hg-cmd">hg copy</command> files, Mercurial updates the
+	dirstate so that it knows what to do with those files when you
+	commit.</para>
+
+      <para>When Mercurial is checking the states of files in the
+	working directory, it first checks a file's modification time.
+	If that has not changed, the file must not have been modified.
+	If the file's size has changed, the file must have been
+	modified.  If the modification time has changed, but the size
+	has not, only then does Mercurial need to read the actual
+	contents of the file to see if they've changed. Storing these
+	few extra pieces of information dramatically reduces the
+	amount of data that Mercurial needs to read, which yields
+	large performance improvements compared to other revision
+	control systems.</para>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch05-daily.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch05-daily.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,490 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:daily">
+  <title>Mercurial in daily use</title>
+
+  <sect1>
+    <title>Telling Mercurial which files to track</title>
+
+    <para>Mercurial does not work with files in your repository unless
+      you tell it to manage them.  The <command role="hg-cmd">hg
+	status</command> command will tell you which files Mercurial
+      doesn't know about; it uses a
+      <quote><literal>?</literal></quote> to display such
+      files.</para>
+
+    <para>To tell Mercurial to track a file, use the <command
+	role="hg-cmd">hg add</command> command.  Once you have added a
+      file, the entry in the output of <command role="hg-cmd">hg
+	status</command> for that file changes from
+      <quote><literal>?</literal></quote> to
+      <quote><literal>A</literal></quote>. <!--
+      &interaction.daily.files.add; --></para>
+
+    <para>After you run a <command role="hg-cmd">hg commit</command>,
+      the files that you added before the commit will no longer be
+      listed in the output of <command role="hg-cmd">hg
+	status</command>.  The reason for this is that <command
+	role="hg-cmd">hg status</command> only tells you about
+      <quote>interesting</quote> files&emdash;those that you have
+      modified or told Mercurial to do something with&emdash;by
+      default.  If you have a repository that contains thousands of
+      files, you will rarely want to know about files that Mercurial
+      is tracking, but that have not changed.  (You can still get this
+      information; we'll return to this later.)</para>
+
+    <para>Once you add a file, Mercurial doesn't do anything with it
+      immediately.  Instead, it will take a snapshot of the file's
+      state the next time you perform a commit.  It will then continue
+      to track the changes you make to the file every time you commit,
+      until you remove the file.</para>
+
+    <sect2>
+      <title>Explicit versus implicit file naming</title>
+
+      <para>A useful behaviour that Mercurial has is that if you pass
+	the name of a directory to a command, every Mercurial command
+	will treat this as <quote>I want to operate on every file in
+	  this directory and its subdirectories</quote>. <!--
+	&interaction.daily.files.add-dir; --> Notice in this example
+	that Mercurial printed the names of the files it added,
+	whereas it didn't do so when we added the file named
+	<filename>a</filename> in the earlier example.</para>
+
+      <para>What's going on is that in the former case, we explicitly
+	named the file to add on the command line, so the assumption
+	that Mercurial makes in such cases is that you know what you
+	were doing, and it doesn't print any output.</para>
+
+      <para>However, when we <emphasis>imply</emphasis> the names of
+	files by giving the name of a directory, Mercurial takes the
+	extra step of printing the name of each file that it does
+	something with.  This makes it more clear what is happening,
+	and reduces the likelihood of a silent and nasty surprise.
+	This behaviour is common to most Mercurial commands.</para>
+
+    </sect2>
+    <sect2>
+      <title>Aside: Mercurial tracks files, not directories</title>
+
+      <para>Mercurial does not track directory information.  Instead,
+	it tracks the path to a file.  Before creating a file, it
+	first creates any missing directory components of the path.
+	After it deletes a file, it then deletes any empty directories
+	that were in the deleted file's path.  This sounds like a
+	trivial distinction, but it has one minor practical
+	consequence: it is not possible to represent a completely
+	empty directory in Mercurial.</para>
+
+      <para>Empty directories are rarely useful, and there are
+	unintrusive workarounds that you can use to achieve an
+	appropriate effect.  The developers of Mercurial thus felt
+	that the complexity that would be required to manage empty
+	directories was not worth the limited benefit this feature
+	would bring.</para>
+
+      <para>If you need an empty directory in your repository, there
+	are a few ways to achieve this. One is to create a directory,
+	then <command role="hg-cmd">hg add</command> a
+	<quote>hidden</quote> file to that directory.  On Unix-like
+	systems, any file name that begins with a period
+	(<quote><literal>.</literal></quote>) is treated as hidden by
+	most commands and GUI tools.  This approach is illustrated
+	below.</para>
+
+<!-- &interaction.daily.files.hidden; -->
+
+      <para>Another way to tackle a need for an empty directory is to
+	simply create one in your automated build scripts before they
+	will need it.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>How to stop tracking a file</title>
+
+    <para>Once you decide that a file no longer belongs in your
+      repository, use the <command role="hg-cmd">hg remove</command>
+      command; this deletes the file, and tells Mercurial to stop
+      tracking it.  A removed file is represented in the output of
+      <command role="hg-cmd">hg status</command> with a
+      <quote><literal>R</literal></quote>. <!--
+      &interaction.daily.files.remove; --></para>
+
+    <para>After you <command role="hg-cmd">hg remove</command> a file,
+      Mercurial will no longer track changes to that file, even if you
+      recreate a file with the same name in your working directory.
+      If you do recreate a file with the same name and want Mercurial
+      to track the new file, simply <command role="hg-cmd">hg
+	add</command> it. Mercurial will know that the newly added
+      file is not related to the old file of the same name.</para>
+
+    <sect2>
+      <title>Removing a file does not affect its history</title>
+
+      <para>It is important to understand that removing a file has
+	only two effects.</para>
+      <itemizedlist>
+	<listitem><para>It removes the current version of the file
+	    from the working directory.</para>
+	</listitem>
+	<listitem><para>It stops Mercurial from tracking changes to
+	    the file, from the time of the next commit.</para>
+	</listitem></itemizedlist>
+      <para>Removing a file <emphasis>does not</emphasis> in any way
+	alter the <emphasis>history</emphasis> of the file.</para>
+
+      <para>If you update the working directory to a changeset in
+	which a file that you have removed was still tracked, it will
+	reappear in the working directory, with the contents it had
+	when you committed that changeset.  If you then update the
+	working directory to a later changeset, in which the file had
+	been removed, Mercurial will once again remove the file from
+	the working directory.</para>
+
+    </sect2>
+    <sect2>
+      <title>Missing files</title>
+
+      <para>Mercurial considers a file that you have deleted, but not
+	used <command role="hg-cmd">hg remove</command> to delete, to
+	be <emphasis>missing</emphasis>.  A missing file is
+	represented with <quote><literal>!</literal></quote> in the
+	output of <command role="hg-cmd">hg status</command>.
+	Mercurial commands will not generally do anything with missing
+	files. <!-- &interaction.daily.files.missing; --></para>
+
+      <para>If your repository contains a file that <command
+	  role="hg-cmd">hg status</command> reports as missing, and
+	you want the file to stay gone, you can run <command
+	  role="hg-cmd">hg remove <option
+	    role="hg-opt-remove">--after</option></command> at any
+	time later on, to tell Mercurial that you really did mean to
+	remove the file. <!-- &interaction.daily.files.remove-after;
+	--></para>
+
+      <para>On the other hand, if you deleted the missing file by
+	accident, give <command role="hg-cmd">hg revert</command> the
+	name of the file to recover.  It will reappear, in unmodified
+	form.</para>
+
+<!-- &interaction.daily.files.recover-missing; -->
+
+    </sect2>
+    <sect2>
+      <title>Aside: why tell Mercurial explicitly to remove a
+	file?</title>
+
+      <para>You might wonder why Mercurial requires you to explicitly
+	tell it that you are deleting a file.  Early during the
+	development of Mercurial, it let you delete a file however you
+	pleased; Mercurial would notice the absence of the file
+	automatically when you next ran a <command role="hg-cmd">hg
+	  commit</command>, and stop tracking the file.  In practice,
+	this made it too easy to accidentally remove a file without
+	noticing.</para>
+
+    </sect2>
+    <sect2>
+      <title>Useful shorthand&emdash;adding and removing files in one
+	step</title>
+
+      <para>Mercurial offers a combination command, <command
+	  role="hg-cmd">hg addremove</command>, that adds untracked
+	files and marks missing files as removed. <!--
+	&interaction.daily.files.addremove; --> The <command
+	  role="hg-cmd">hg commit</command> command also provides a
+	<option role="hg-opt-commit">-A</option> option that performs
+	this same add-and-remove, immediately followed by a commit.
+	<!-- &interaction.daily.files.commit-addremove; --></para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Copying files</title>
+
+    <para>Mercurial provides a <command role="hg-cmd">hg
+	copy</command> command that lets you make a new copy of a
+      file.  When you copy a file using this command, Mercurial makes
+      a record of the fact that the new file is a copy of the original
+      file.  It treats these copied files specially when you merge
+      your work with someone else's.</para>
+
+    <sect2>
+      <title>The results of copying during a merge</title>
+
+      <para>What happens during a merge is that changes
+	<quote>follow</quote> a copy.  To best illustrate what this
+	means, let's create an example.  We'll start with the usual
+	tiny repository that contains a single file. <!--
+	&interaction.daily.copy.init; --> We need to do some work in
+	parallel, so that we'll have something to merge.  So let's
+	clone our repository. <!-- &interaction.daily.copy.clone; -->
+	Back in our initial repository, let's use the <command
+	  role="hg-cmd">hg copy</command> command to make a copy of
+	the first file we created. <!-- &interaction.daily.copy.copy;
+	--></para>
+
+      <para>If we look at the output of the <command role="hg-cmd">hg
+	  status</command> command afterwards, the copied file looks
+	just like a normal added file. <!--
+	&interaction.daily.copy.status; --> But if we pass the <option
+	  role="hg-opt-status">-C</option> option to <command
+	  role="hg-cmd">hg status</command>, it prints another line of
+	output: this is the file that our newly-added file was copied
+	<emphasis>from</emphasis>. <!--
+	&interaction.daily.copy.status-copy; --></para>
+
+      <para>Now, back in the repository we cloned, let's make a change
+	in parallel.  We'll add a line of content to the original file
+	that we created. <!-- &interaction.daily.copy.other; --> Now
+	we have a modified <filename>file</filename> in this
+	repository.  When we pull the changes from the first
+	repository, and merge the two heads, Mercurial will propagate
+	the changes that we made locally to <filename>file</filename>
+	into its copy, <filename>new-file</filename>. <!--
+	&interaction.daily.copy.merge; --></para>
+
+    </sect2>
+    <sect2 id="sec:daily:why-copy">
+      <title>Why should changes follow copies?</title>
+
+      <para>This behaviour, of changes to a file propagating out to
+	copies of the file, might seem esoteric, but in most cases
+	it's highly desirable.</para>
+
+      <para>First of all, remember that this propagation
+	<emphasis>only</emphasis> happens when you merge.  So if you
+	<command role="hg-cmd">hg copy</command> a file, and
+	subsequently modify the original file during the normal course
+	of your work, nothing will happen.</para>
+
+      <para>The second thing to know is that modifications will only
+	propagate across a copy as long as the repository that you're
+	pulling changes from <emphasis>doesn't know</emphasis> about
+	the copy.</para>
+
+      <para>The reason that Mercurial does this is as follows.  Let's
+	say I make an important bug fix in a source file, and commit
+	my changes. Meanwhile, you've decided to <command
+	  role="hg-cmd">hg copy</command> the file in your repository,
+	without knowing about the bug or having seen the fix, and you
+	have started hacking on your copy of the file.</para>
+
+      <para>If you pulled and merged my changes, and Mercurial
+	<emphasis>didn't</emphasis> propagate changes across copies,
+	your source file would now contain the bug, and unless you
+	remembered to propagate the bug fix by hand, the bug would
+	<emphasis>remain</emphasis> in your copy of the file.</para>
+
+      <para>By automatically propagating the change that fixed the bug
+	from the original file to the copy, Mercurial prevents this
+	class of problem. To my knowledge, Mercurial is the
+	<emphasis>only</emphasis> revision control system that
+	propagates changes across copies like this.</para>
+
+      <para>Once your change history has a record that the copy and
+	subsequent merge occurred, there's usually no further need to
+	propagate changes from the original file to the copied file,
+	and that's why Mercurial only propagates changes across copies
+	until this point, and no further.</para>
+
+    </sect2>
+    <sect2>
+      <title>How to make changes <emphasis>not</emphasis> follow a
+	copy</title>
+
+      <para>If, for some reason, you decide that this business of
+	automatically propagating changes across copies is not for
+	you, simply use your system's normal file copy command (on
+	Unix-like systems, that's <command>cp</command>) to make a
+	copy of a file, then <command role="hg-cmd">hg add</command>
+	the new copy by hand.  Before you do so, though, please do
+	reread section <xref linkend="sec:daily:why-copy"/>, and make
+	an informed
+	decision that this behaviour is not appropriate to your
+	specific case.</para>
+
+    </sect2>
+    <sect2>
+      <title>Behaviour of the <command role="hg-cmd">hg copy</command>
+	command</title>
+
+      <para>When you use the <command role="hg-cmd">hg copy</command>
+	command, Mercurial makes a copy of each source file as it
+	currently stands in the working directory.  This means that if
+	you make some modifications to a file, then <command
+	  role="hg-cmd">hg copy</command> it without first having
+	committed those changes, the new copy will also contain the
+	modifications you have made up until that point.  (I find this
+	behaviour a little counterintuitive, which is why I mention it
+	here.)</para>
+
+      <para>The <command role="hg-cmd">hg copy</command> command acts
+	similarly to the Unix <command>cp</command> command (you can
+	use the <command role="hg-cmd">hg cp</command> alias if you
+	prefer).  The last argument is the
+	<emphasis>destination</emphasis>, and all prior arguments are
+	<emphasis>sources</emphasis>.  If you pass it a single file as
+	the source, and the destination does not exist, it creates a
+	new file with that name. <!-- &interaction.daily.copy.simple;
+	--> If the destination is a directory, Mercurial copies its
+	sources into that directory. <!--
+	&interaction.daily.copy.dir-dest; --> Copying a directory is
+	recursive, and preserves the directory structure of the
+	source. <!-- &interaction.daily.copy.dir-src; --> If the
+	source and destination are both directories, the source tree
+	is recreated in the destination directory. <!--
+	&interaction.daily.copy.dir-src-dest; --></para>
+
+      <para>As with the <command role="hg-cmd">hg rename</command>
+	command, if you copy a file manually and then want Mercurial
+	to know that you've copied the file, simply use the <option
+	  role="hg-opt-copy">--after</option> option to <command
+	  role="hg-cmd">hg copy</command>. <!--
+	&interaction.daily.copy.after; --></para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Renaming files</title>
+
+    <para>It's rather more common to need to rename a file than to
+      make a copy of it.  The reason I discussed the <command
+	role="hg-cmd">hg copy</command> command before talking about
+      renaming files is that Mercurial treats a rename in essentially
+      the same way as a copy.  Therefore, knowing what Mercurial does
+      when you copy a file tells you what to expect when you rename a
+      file.</para>
+
+    <para>When you use the <command role="hg-cmd">hg rename</command>
+      command, Mercurial makes a copy of each source file, then
+      deletes it and marks the file as removed. <!--
+      &interaction.daily.rename.rename; --> The <command
+	role="hg-cmd">hg status</command> command shows the newly
+      copied file as added, and the copied-from file as removed. <!--
+      &interaction.daily.rename.status; --> As with the results of a
+      <command role="hg-cmd">hg copy</command>, we must use the
+      <option role="hg-opt-status">-C</option> option to <command
+	role="hg-cmd">hg status</command> to see that the added file
+      is really being tracked by Mercurial as a copy of the original,
+      now removed, file. <!-- &interaction.daily.rename.status-copy;
+      --></para>
+
+    <para>As with <command role="hg-cmd">hg remove</command> and
+      <command role="hg-cmd">hg copy</command>, you can tell Mercurial
+      about a rename after the fact using the <option
+	role="hg-opt-rename">--after</option> option.  In most other
+      respects, the behaviour of the <command role="hg-cmd">hg
+	rename</command> command, and the options it accepts, are
+      similar to the <command role="hg-cmd">hg copy</command>
+      command.</para>
+
+    <sect2>
+      <title>Renaming files and merging changes</title>
+
+      <para>Since Mercurial's rename is implemented as
+	copy-and-remove, the same propagation of changes happens when
+	you merge after a rename as after a copy.</para>
+
+      <para>If I modify a file, and you rename it to a new name, and
+	then we merge our respective changes, my modifications to the
+	file under its original name will be propagated into the file
+	under its new name. (This is something you might expect to
+	<quote>simply work,</quote> but not all revision control
+	systems actually do this.)</para>
+
+      <para>Whereas having changes follow a copy is a feature where
+	you can perhaps nod and say <quote>yes, that might be
+	  useful,</quote> it should be clear that having them follow a
+	rename is definitely important.  Without this facility, it
+	would simply be too easy for changes to become orphaned when
+	files are renamed.</para>
+
+    </sect2>
+    <sect2>
+      <title>Divergent renames and merging</title>
+
+      <para>The case of diverging names occurs when two developers
+	start with a file&emdash;let's call it
+	<filename>foo</filename>&emdash;in their respective
+	repositories.</para>
+
+      <para><!-- &interaction.rename.divergent.clone; --> Anne renames
+	the file to <filename>bar</filename>. <!--
+	&interaction.rename.divergent.rename.anne; --> Meanwhile, Bob
+	renames it to <filename>quux</filename>. <!--
+	&interaction.rename.divergent.rename.bob; --></para>
+
+      <para>I like to think of this as a conflict because each
+	developer has expressed different intentions about what the
+	file ought to be named.</para>
+
+      <para>What do you think should happen when they merge their
+	work? Mercurial's actual behaviour is that it always preserves
+	<emphasis>both</emphasis> names when it merges changesets that
+	contain divergent renames. <!--
+	&interaction.rename.divergent.merge; --></para>
+
+      <para>Notice that Mercurial does warn about the divergent
+	renames, but it leaves it up to you to do something about the
+	divergence after the merge.</para>
+
+    </sect2>
+    <sect2>
+      <title>Convergent renames and merging</title>
+
+      <para>Another kind of rename conflict occurs when two people
+	choose to rename different <emphasis>source</emphasis> files
+	to the same <emphasis>destination</emphasis>. In this case,
+	Mercurial runs its normal merge machinery, and lets you guide
+	it to a suitable resolution.</para>
+
+    </sect2>
+    <sect2>
+      <title>Other name-related corner cases</title>
+
+      <para>Mercurial has a longstanding bug in which it fails to
+	handle a merge where one side has a file with a given name,
+	while another has a directory with the same name.  This is
+	documented as <ulink role="hg-bug"
+	  url="http://www.selenic.com/mercurial/bts/issue29">issue
+	  29</ulink>. <!-- &interaction.issue29.go; --></para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Recovering from mistakes</title>
+
+    <para>Mercurial has some useful commands that will help you to
+      recover from some common mistakes.</para>
+
+    <para>The <command role="hg-cmd">hg revert</command> command lets
+      you undo changes that you have made to your working directory.
+      For example, if you <command role="hg-cmd">hg add</command> a
+      file by accident, just run <command role="hg-cmd">hg
+	revert</command> with the name of the file you added, and
+      while the file won't be touched in any way, it won't be tracked
+      for adding by Mercurial any longer, either.  You can also use
+      <command role="hg-cmd">hg revert</command> to get rid of
+      erroneous changes to a file.</para>
+
+    <para>It's useful to remember that the <command role="hg-cmd">hg
+	revert</command> command is useful for changes that you have
+      not yet committed.  Once you've committed a change, if you
+      decide it was a mistake, you can still do something about it,
+      though your options may be more limited.</para>
+
+    <para>For more information about the <command role="hg-cmd">hg
+	revert</command> command, and details about how to deal with
+      changes you have already committed, see chapter <xref
+	linkend="chap:undo"/>.</para>
+
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch06-collab.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch06-collab.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,1415 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="cha:collab">
+  <title>Collaborating with other people</title>
+
+  <para>As a completely decentralised tool, Mercurial doesn't impose
+    any policy on how people ought to work with each other.  However,
+    if you're new to distributed revision control, it helps to have
+    some tools and examples in mind when you're thinking about
+    possible workflow models.</para>
+
+  <sect1>
+    <title>Mercurial's web interface</title>
+
+    <para>Mercurial has a powerful web interface that provides several
+      useful capabilities.</para>
+
+    <para>For interactive use, the web interface lets you browse a
+      single repository or a collection of repositories.  You can view
+      the history of a repository, examine each change (comments and
+      diffs), and view the contents of each directory and file.</para>
+
+    <para>Also for human consumption, the web interface provides an
+      RSS feed of the changes in a repository.  This lets you
+      <quote>subscribe</quote> to a repository using your favourite
+      feed reader, and be automatically notified of activity in that
+      repository as soon as it happens.  I find this capability much
+      more convenient than the model of subscribing to a mailing list
+      to which notifications are sent, as it requires no additional
+      configuration on the part of whoever is serving the
+      repository.</para>
+
+    <para>The web interface also lets remote users clone a repository,
+      pull changes from it, and (when the server is configured to
+      permit it) push changes back to it.  Mercurial's HTTP tunneling
+      protocol aggressively compresses data, so that it works
+      efficiently even over low-bandwidth network connections.</para>
+
+    <para>The easiest way to get started with the web interface is to
+      use your web browser to visit an existing repository, such as
+      the master Mercurial repository at <ulink
+	url="http://www.selenic.com/repo/hg?style=gitweb">http://www.selenic.com/repo/hg?style=gitweb</ulink>.</para>
+
+    <para>If you're interested in providing a web interface to your
+      own repositories, Mercurial provides two ways to do this.  The
+      first is using the <command role="hg-cmd">hg serve</command>
+      command, which is best suited to short-term
+      <quote>lightweight</quote> serving.  See section <xref
+	linkend="sec:collab:serve"/> below for details of how to use
+      this command.  If you have a long-lived repository that you'd
+      like to make permanently available, Mercurial has built-in
+      support for the CGI (Common Gateway Interface) standard, which
+      all common web servers support.  See section <xref
+	linkend="sec:collab:cgi"/> for details of CGI
+      configuration.</para>
+
+  </sect1>
+  <sect1>
+    <title>Collaboration models</title>
+
+    <para>With a suitably flexible tool, making decisions about
+      workflow is much more of a social engineering challenge than a
+      technical one. Mercurial imposes few limitations on how you can
+      structure the flow of work in a project, so it's up to you and
+      your group to set up and live with a model that matches your own
+      particular needs.</para>
+
+    <sect2>
+      <title>Factors to keep in mind</title>
+
+      <para>The most important aspect of any model that you must keep
+	in mind is how well it matches the needs and capabilities of
+	the people who will be using it.  This might seem
+	self-evident; even so, you still can't afford to forget it for
+	a moment.</para>
+
+      <para>I once put together a workflow model that seemed to make
+	perfect sense to me, but that caused a considerable amount of
+	consternation and strife within my development team.  In spite
+	of my attempts to explain why we needed a complex set of
+	branches, and how changes ought to flow between them, a few
+	team members revolted.  Even though they were smart people,
+	they didn't want to pay attention to the constraints we were
+	operating under, or face the consequences of those constraints
+	in the details of the model that I was advocating.</para>
+
+      <para>Don't sweep foreseeable social or technical problems under
+	the rug. Whatever scheme you put into effect, you should plan
+	for mistakes and problem scenarios.  Consider adding automated
+	machinery to prevent, or quickly recover from, trouble that
+	you can anticipate.  As an example, if you intend to have a
+	branch with not-for-release changes in it, you'd do well to
+	think early about the possibility that someone might
+	accidentally merge those changes into a release branch.  You
+	could avoid this particular problem by writing a hook that
+	prevents changes from being merged from an inappropriate
+	branch.</para>
+
+    </sect2>
+    <sect2>
+      <title>Informal anarchy</title>
+
+      <para>I wouldn't suggest an <quote>anything goes</quote>
+	approach as something sustainable, but it's a model that's
+	easy to grasp, and it works perfectly well in a few unusual
+	situations.</para>
+
+      <para>As one example, many projects have a loose-knit group of
+	collaborators who rarely physically meet each other.  Some
+	groups like to overcome the isolation of working at a distance
+	by organising occasional <quote>sprints</quote>.  In a sprint,
+	a number of people get together in a single location (a
+	company's conference room, a hotel meeting room, that kind of
+	place) and spend several days more or less locked in there,
+	hacking intensely on a handful of projects.</para>
+
+      <para>A sprint is the perfect place to use the <command
+	  role="hg-cmd">hg serve</command> command, since <command
+	  role="hg-cmd">hg serve</command> does not requires any fancy
+	server infrastructure.  You can get started with <command
+	  role="hg-cmd">hg serve</command> in moments, by reading
+	section <xref linkend="sec:collab:serve"/> below.  Then simply
+	tell
+	the person next to you that you're running a server, send the
+	URL to them in an instant message, and you immediately have a
+	quick-turnaround way to work together.  They can type your URL
+	into their web browser and quickly review your changes; or
+	they can pull a bugfix from you and verify it; or they can
+	clone a branch containing a new feature and try it out.</para>
+
+      <para>The charm, and the problem, with doing things in an ad hoc
+	fashion like this is that only people who know about your
+	changes, and where they are, can see them.  Such an informal
+	approach simply doesn't scale beyond a handful people, because
+	each individual needs to know about $n$ different repositories
+	to pull from.</para>
+
+    </sect2>
+    <sect2>
+      <title>A single central repository</title>
+
+      <para>For smaller projects migrating from a centralised revision
+	control tool, perhaps the easiest way to get started is to
+	have changes flow through a single shared central repository.
+	This is also the most common <quote>building block</quote> for
+	more ambitious workflow schemes.</para>
+
+      <para>Contributors start by cloning a copy of this repository.
+	They can pull changes from it whenever they need to, and some
+	(perhaps all) developers have permission to push a change back
+	when they're ready for other people to see it.</para>
+
+      <para>Under this model, it can still often make sense for people
+	to pull changes directly from each other, without going
+	through the central repository.  Consider a case in which I
+	have a tentative bug fix, but I am worried that if I were to
+	publish it to the central repository, it might subsequently
+	break everyone else's trees as they pull it.  To reduce the
+	potential for damage, I can ask you to clone my repository
+	into a temporary repository of your own and test it.  This
+	lets us put off publishing the potentially unsafe change until
+	it has had a little testing.</para>
+
+      <para>In this kind of scenario, people usually use the
+	<command>ssh</command> protocol to securely push changes to
+	the central repository, as documented in section <xref
+	  linkend="sec:collab:ssh"/>.  It's also
+	usual to publish a read-only copy of the repository over HTTP
+	using CGI, as in section <xref linkend="sec:collab:cgi"/>.
+	Publishing over HTTP
+	satisfies the needs of people who don't have push access, and
+	those who want to use web browsers to browse the repository's
+	history.</para>
+
+    </sect2>
+    <sect2>
+      <title>Working with multiple branches</title>
+
+      <para>Projects of any significant size naturally tend to make
+	progress on several fronts simultaneously.  In the case of
+	software, it's common for a project to go through periodic
+	official releases.  A release might then go into
+	<quote>maintenance mode</quote> for a while after its first
+	publication; maintenance releases tend to contain only bug
+	fixes, not new features.  In parallel with these maintenance
+	releases, one or more future releases may be under
+	development.  People normally use the word
+	<quote>branch</quote> to refer to one of these many slightly
+	different directions in which development is
+	proceeding.</para>
+
+      <para>Mercurial is particularly well suited to managing a number
+	of simultaneous, but not identical, branches.  Each
+	<quote>development direction</quote> can live in its own
+	central repository, and you can merge changes from one to
+	another as the need arises.  Because repositories are
+	independent of each other, unstable changes in a development
+	branch will never affect a stable branch unless someone
+	explicitly merges those changes in.</para>
+
+      <para>Here's an example of how this can work in practice.  Let's
+	say you have one <quote>main branch</quote> on a central
+	server. <!-- &interaction.branching.init; --> People clone it,
+	make changes locally, test them, and push them back.</para>
+
+      <para>Once the main branch reaches a release milestone, you can
+	use the <command role="hg-cmd">hg tag</command> command to
+	give a permanent name to the milestone revision. <!--
+	&interaction.branching.tag; --> Let's say some ongoing
+	development occurs on the main branch. <!--
+	&interaction.branching.main; --> Using the tag that was
+	recorded at the milestone, people who clone that repository at
+	any time in the future can use <command role="hg-cmd">hg
+	  update</command> to get a copy of the working directory
+	exactly as it was when that tagged revision was committed.
+	<!-- &interaction.branching.update; --></para>
+
+      <para>In addition, immediately after the main branch is tagged,
+	someone can then clone the main branch on the server to a new
+	<quote>stable</quote> branch, also on the server. <!--
+	&interaction.branching.clone; --></para>
+
+      <para>Someone who needs to make a change to the stable branch
+	can then clone <emphasis>that</emphasis> repository, make
+	their changes, commit, and push their changes back there. <!--
+	&interaction.branching.stable; --> Because Mercurial
+	repositories are independent, and Mercurial doesn't move
+	changes around automatically, the stable and main branches are
+	<emphasis>isolated</emphasis> from each other.  The changes
+	that you made on the main branch don't <quote>leak</quote> to
+	the stable branch, and vice versa.</para>
+
+      <para>You'll often want all of your bugfixes on the stable
+	branch to show up on the main branch, too.  Rather than
+	rewrite a bugfix on the main branch, you can simply pull and
+	merge changes from the stable to the main branch, and
+	Mercurial will bring those bugfixes in for you. <!--
+	&interaction.branching.merge; --> The main branch will still
+	contain changes that are not on the stable branch, but it will
+	also contain all of the bugfixes from the stable branch.  The
+	stable branch remains unaffected by these changes.</para>
+
+    </sect2>
+    <sect2>
+      <title>Feature branches</title>
+
+      <para>For larger projects, an effective way to manage change is
+	to break up a team into smaller groups.  Each group has a
+	shared branch of its own, cloned from a single
+	<quote>master</quote> branch used by the entire project.
+	People working on an individual branch are typically quite
+	isolated from developments on other branches.</para>
+
+      <informalfigure id="fig:collab:feature-branches">
+	<mediaobject><imageobject><imagedata
+				    fileref="feature-branches"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Feature
+	      branches</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>When a particular feature is deemed to be in suitable
+	shape, someone on that feature team pulls and merges from the
+	master branch into the feature branch, then pushes back up to
+	the master branch.</para>
+
+    </sect2>
+    <sect2>
+      <title>The release train</title>
+
+      <para>Some projects are organised on a <quote>train</quote>
+	basis: a release is scheduled to happen every few months, and
+	whatever features are ready when the <quote>train</quote> is
+	ready to leave are allowed in.</para>
+
+      <para>This model resembles working with feature branches.  The
+	difference is that when a feature branch misses a train,
+	someone on the feature team pulls and merges the changes that
+	went out on that train release into the feature branch, and
+	the team continues its work on top of that release so that
+	their feature can make the next release.</para>
+
+    </sect2>
+    <sect2>
+      <title>The Linux kernel model</title>
+
+      <para>The development of the Linux kernel has a shallow
+	hierarchical structure, surrounded by a cloud of apparent
+	chaos.  Because most Linux developers use
+	<command>git</command>, a distributed revision control tool
+	with capabilities similar to Mercurial, it's useful to
+	describe the way work flows in that environment; if you like
+	the ideas, the approach translates well across tools.</para>
+
+      <para>At the center of the community sits Linus Torvalds, the
+	creator of Linux.  He publishes a single source repository
+	that is considered the <quote>authoritative</quote> current
+	tree by the entire developer community. Anyone can clone
+	Linus's tree, but he is very choosy about whose trees he pulls
+	from.</para>
+
+      <para>Linus has a number of <quote>trusted lieutenants</quote>.
+	As a general rule, he pulls whatever changes they publish, in
+	most cases without even reviewing those changes.  Some of
+	those lieutenants are generally agreed to be
+	<quote>maintainers</quote>, responsible for specific
+	subsystems within the kernel.  If a random kernel hacker wants
+	to make a change to a subsystem that they want to end up in
+	Linus's tree, they must find out who the subsystem's
+	maintainer is, and ask that maintainer to take their change.
+	If the maintainer reviews their changes and agrees to take
+	them, they'll pass them along to Linus in due course.</para>
+
+      <para>Individual lieutenants have their own approaches to
+	reviewing, accepting, and publishing changes; and for deciding
+	when to feed them to Linus.  In addition, there are several
+	well known branches that people use for different purposes.
+	For example, a few people maintain <quote>stable</quote>
+	repositories of older versions of the kernel, to which they
+	apply critical fixes as needed.  Some maintainers publish
+	multiple trees: one for experimental changes; one for changes
+	that they are about to feed upstream; and so on.  Others just
+	publish a single tree.</para>
+
+      <para>This model has two notable features.  The first is that
+	it's <quote>pull only</quote>.  You have to ask, convince, or
+	beg another developer to take a change from you, because there
+	are almost no trees to which more than one person can push,
+	and there's no way to push changes into a tree that someone
+	else controls.</para>
+
+      <para>The second is that it's based on reputation and acclaim.
+	If you're an unknown, Linus will probably ignore changes from
+	you without even responding.  But a subsystem maintainer will
+	probably review them, and will likely take them if they pass
+	their criteria for suitability. The more <quote>good</quote>
+	changes you contribute to a maintainer, the more likely they
+	are to trust your judgment and accept your changes.  If you're
+	well-known and maintain a long-lived branch for something
+	Linus hasn't yet accepted, people with similar interests may
+	pull your changes regularly to keep up with your work.</para>
+
+      <para>Reputation and acclaim don't necessarily cross subsystem
+	or <quote>people</quote> boundaries.  If you're a respected
+	but specialised storage hacker, and you try to fix a
+	networking bug, that change will receive a level of scrutiny
+	from a network maintainer comparable to a change from a
+	complete stranger.</para>
+
+      <para>To people who come from more orderly project backgrounds,
+	the comparatively chaotic Linux kernel development process
+	often seems completely insane.  It's subject to the whims of
+	individuals; people make sweeping changes whenever they deem
+	it appropriate; and the pace of development is astounding.
+	And yet Linux is a highly successful, well-regarded piece of
+	software.</para>
+
+    </sect2>
+    <sect2>
+      <title>Pull-only versus shared-push collaboration</title>
+
+      <para>A perpetual source of heat in the open source community is
+	whether a development model in which people only ever pull
+	changes from others is <quote>better than</quote> one in which
+	multiple people can push changes to a shared
+	repository.</para>
+
+      <para>Typically, the backers of the shared-push model use tools
+	that actively enforce this approach.  If you're using a
+	centralised revision control tool such as Subversion, there's
+	no way to make a choice over which model you'll use: the tool
+	gives you shared-push, and if you want to do anything else,
+	you'll have to roll your own approach on top (such as applying
+	a patch by hand).</para>
+
+      <para>A good distributed revision control tool, such as
+	Mercurial, will support both models.  You and your
+	collaborators can then structure how you work together based
+	on your own needs and preferences, not on what contortions
+	your tools force you into.</para>
+
+    </sect2>
+    <sect2>
+      <title>Where collaboration meets branch management</title>
+
+      <para>Once you and your team set up some shared repositories and
+	start propagating changes back and forth between local and
+	shared repos, you begin to face a related, but slightly
+	different challenge: that of managing the multiple directions
+	in which your team may be moving at once.  Even though this
+	subject is intimately related to how your team collaborates,
+	it's dense enough to merit treatment of its own, in chapter
+	<xref linkend="chap:branch"/>.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>The technical side of sharing</title>
+
+    <para>The remainder of this chapter is devoted to the question of
+      serving data to your collaborators.</para>
+
+  </sect1>
+  <sect1 id="sec:collab:serve">
+    <title>Informal sharing with <command role="hg-cmd">hg
+	serve</command></title>
+
+    <para>Mercurial's <command role="hg-cmd">hg serve</command>
+      command is wonderfully suited to small, tight-knit, and
+      fast-paced group environments.  It also provides a great way to
+      get a feel for using Mercurial commands over a network.</para>
+
+    <para>Run <command role="hg-cmd">hg serve</command> inside a
+      repository, and in under a second it will bring up a specialised
+      HTTP server; this will accept connections from any client, and
+      serve up data for that repository until you terminate it.
+      Anyone who knows the URL of the server you just started, and can
+      talk to your computer over the network, can then use a web
+      browser or Mercurial to read data from that repository.  A URL
+      for a <command role="hg-cmd">hg serve</command> instance running
+      on a laptop is likely to look something like
+      <literal>http://my-laptop.local:8000/</literal>.</para>
+
+    <para>The <command role="hg-cmd">hg serve</command> command is
+      <emphasis>not</emphasis> a general-purpose web server. It can do
+      only two things:</para>
+    <itemizedlist>
+      <listitem><para>Allow people to browse the history of the
+	  repository it's serving, from their normal web
+	  browsers.</para>
+      </listitem>
+      <listitem><para>Speak Mercurial's wire protocol, so that people
+	  can <command role="hg-cmd">hg clone</command> or <command
+	    role="hg-cmd">hg pull</command> changes from that
+	  repository.</para>
+      </listitem></itemizedlist>
+    <para>In particular, <command role="hg-cmd">hg serve</command>
+      won't allow remote users to <emphasis>modify</emphasis> your
+      repository.  It's intended for read-only use.</para>
+
+    <para>If you're getting started with Mercurial, there's nothing to
+      prevent you from using <command role="hg-cmd">hg serve</command>
+      to serve up a repository on your own computer, then use commands
+      like <command role="hg-cmd">hg clone</command>, <command
+	role="hg-cmd">hg incoming</command>, and so on to talk to that
+      server as if the repository was hosted remotely. This can help
+      you to quickly get acquainted with using commands on
+      network-hosted repositories.</para>
+
+    <sect2>
+      <title>A few things to keep in mind</title>
+
+      <para>Because it provides unauthenticated read access to all
+	clients, you should only use <command role="hg-cmd">hg
+	  serve</command> in an environment where you either don't
+	care, or have complete control over, who can access your
+	network and pull data from your repository.</para>
+
+      <para>The <command role="hg-cmd">hg serve</command> command
+	knows nothing about any firewall software you might have
+	installed on your system or network.  It cannot detect or
+	control your firewall software.  If other people are unable to
+	talk to a running <command role="hg-cmd">hg serve</command>
+	instance, the second thing you should do
+	(<emphasis>after</emphasis> you make sure that they're using
+	the correct URL) is check your firewall configuration.</para>
+
+      <para>By default, <command role="hg-cmd">hg serve</command>
+	listens for incoming connections on port 8000.  If another
+	process is already listening on the port you want to use, you
+	can specify a different port to listen on using the <option
+	  role="hg-opt-serve">-p</option> option.</para>
+
+      <para>Normally, when <command role="hg-cmd">hg serve</command>
+	starts, it prints no output, which can be a bit unnerving.  If
+	you'd like to confirm that it is indeed running correctly, and
+	find out what URL you should send to your collaborators, start
+	it with the <option role="hg-opt-global">-v</option>
+	option.</para>
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:collab:ssh">
+    <title>Using the Secure Shell (ssh) protocol</title>
+
+    <para>You can pull and push changes securely over a network
+      connection using the Secure Shell (<literal>ssh</literal>)
+      protocol.  To use this successfully, you may have to do a little
+      bit of configuration on the client or server sides.</para>
+
+    <para>If you're not familiar with ssh, it's a network protocol
+      that lets you securely communicate with another computer.  To
+      use it with Mercurial, you'll be setting up one or more user
+      accounts on a server so that remote users can log in and execute
+      commands.</para>
+
+    <para>(If you <emphasis>are</emphasis> familiar with ssh, you'll
+      probably find some of the material that follows to be elementary
+      in nature.)</para>
+
+    <sect2>
+      <title>How to read and write ssh URLs</title>
+
+      <para>An ssh URL tends to look like this:</para>
+      <programlisting>ssh://bos@hg.serpentine.com:22/hg/hgbook</programlisting>
+      <orderedlist>
+	<listitem><para>The <quote><literal>ssh://</literal></quote>
+	    part tells Mercurial to use the ssh protocol.</para>
+	</listitem>
+	<listitem><para>The <quote><literal>bos@</literal></quote>
+	    component indicates what username to log into the server
+	    as.  You can leave this out if the remote username is the
+	    same as your local username.</para>
+	</listitem>
+	<listitem><para>The
+	    <quote><literal>hg.serpentine.com</literal></quote> gives
+	    the hostname of the server to log into.</para>
+	</listitem>
+	<listitem><para>The <quote>:22</quote> identifies the port
+	    number to connect to the server on.  The default port is
+	    22, so you only need to specify this part if you're
+	    <emphasis>not</emphasis> using port 22.</para>
+	</listitem>
+	<listitem><para>The remainder of the URL is the local path to
+	    the repository on the server.</para>
+	</listitem></orderedlist>
+
+      <para>There's plenty of scope for confusion with the path
+	component of ssh URLs, as there is no standard way for tools
+	to interpret it.  Some programs behave differently than others
+	when dealing with these paths. This isn't an ideal situation,
+	but it's unlikely to change.  Please read the following
+	paragraphs carefully.</para>
+
+      <para>Mercurial treats the path to a repository on the server as
+	relative to the remote user's home directory.  For example, if
+	user <literal>foo</literal> on the server has a home directory
+	of <filename class="directory">/home/foo</filename>, then an
+	ssh URL that contains a path component of <filename
+	  class="directory">bar</filename> <emphasis>really</emphasis>
+	refers to the directory <filename
+	  class="directory">/home/foo/bar</filename>.</para>
+
+      <para>If you want to specify a path relative to another user's
+	home directory, you can use a path that starts with a tilde
+	character followed by the user's name (let's call them
+	<literal>otheruser</literal>), like this.</para>
+      <programlisting>ssh://server/~otheruser/hg/repo</programlisting>
+
+      <para>And if you really want to specify an
+	<emphasis>absolute</emphasis> path on the server, begin the
+	path component with two slashes, as in this example.</para>
+      <programlisting>ssh://server//absolute/path</programlisting>
+
+    </sect2>
+    <sect2>
+      <title>Finding an ssh client for your system</title>
+
+      <para>Almost every Unix-like system comes with OpenSSH
+	preinstalled.  If you're using such a system, run
+	<literal>which ssh</literal> to find out if the
+	<command>ssh</command> command is installed (it's usually in
+	<filename class="directory">/usr/bin</filename>).  In the
+	unlikely event that it isn't present, take a look at your
+	system documentation to figure out how to install it.</para>
+
+      <para>On Windows, you'll first need to download a suitable ssh
+	client.  There are two alternatives.</para>
+      <itemizedlist>
+	<listitem><para>Simon Tatham's excellent PuTTY package
+	    <citation>web:putty</citation> provides a complete suite
+	    of ssh client commands.</para>
+	</listitem>
+	<listitem><para>If you have a high tolerance for pain, you can
+	    use the Cygwin port of OpenSSH.</para>
+	</listitem></itemizedlist>
+      <para>In either case, you'll need to edit your \hgini\ file to
+	tell Mercurial where to find the actual client command.  For
+	example, if you're using PuTTY, you'll need to use the
+	<command>plink</command> command as a command-line ssh
+	client.</para>
+      <programlisting>[ui] ssh = C:/path/to/plink.exe -ssh -i
+	"C:/path/to/my/private/key"</programlisting>
+
+      <note>
+	<para>  The path to <command>plink</command> shouldn't contain
+	  any whitespace characters, or Mercurial may not be able to
+	  run it correctly (so putting it in <filename
+	    class="directory">C:\\Program Files</filename> is probably
+	  not a good idea).</para>
+      </note>
+
+    </sect2>
+    <sect2>
+      <title>Generating a key pair</title>
+
+      <para>To avoid the need to repetitively type a password every
+	time you need to use your ssh client, I recommend generating a
+	key pair.  On a Unix-like system, the
+	<command>ssh-keygen</command> command will do the trick. On
+	Windows, if you're using PuTTY, the
+	<command>puttygen</command> command is what you'll
+	need.</para>
+
+      <para>When you generate a key pair, it's usually
+	<emphasis>highly</emphasis> advisable to protect it with a
+	passphrase.  (The only time that you might not want to do this
+	is when you're using the ssh protocol for automated tasks on a
+	secure network.)</para>
+
+      <para>Simply generating a key pair isn't enough, however.
+	You'll need to add the public key to the set of authorised
+	keys for whatever user you're logging in remotely as.  For
+	servers using OpenSSH (the vast majority), this will mean
+	adding the public key to a list in a file called <filename
+	  role="special">authorized_keys</filename> in their <filename
+	  role="special" class="directory">.ssh</filename>
+	directory.</para>
+
+      <para>On a Unix-like system, your public key will have a
+	<filename>.pub</filename> extension.  If you're using
+	<command>puttygen</command> on Windows, you can save the
+	public key to a file of your choosing, or paste it from the
+	window it's displayed in straight into the <filename
+	  role="special">authorized_keys</filename> file.</para>
+
+    </sect2>
+    <sect2>
+      <title>Using an authentication agent</title>
+
+      <para>An authentication agent is a daemon that stores
+	passphrases in memory (so it will forget passphrases if you
+	log out and log back in again). An ssh client will notice if
+	it's running, and query it for a passphrase.  If there's no
+	authentication agent running, or the agent doesn't store the
+	necessary passphrase, you'll have to type your passphrase
+	every time Mercurial tries to communicate with a server on
+	your behalf (e.g. whenever you pull or push changes).</para>
+
+      <para>The downside of storing passphrases in an agent is that
+	it's possible for a well-prepared attacker to recover the
+	plain text of your passphrases, in some cases even if your
+	system has been power-cycled. You should make your own
+	judgment as to whether this is an acceptable risk.  It
+	certainly saves a lot of repeated typing.</para>
+
+      <para>On Unix-like systems, the agent is called
+	<command>ssh-agent</command>, and it's often run automatically
+	for you when you log in.  You'll need to use the
+	<command>ssh-add</command> command to add passphrases to the
+	agent's store.  On Windows, if you're using PuTTY, the
+	<command>pageant</command> command acts as the agent.  It adds
+	an icon to your system tray that will let you manage stored
+	passphrases.</para>
+
+    </sect2>
+    <sect2>
+      <title>Configuring the server side properly</title>
+
+      <para>Because ssh can be fiddly to set up if you're new to it,
+	there's a variety of things that can go wrong.  Add Mercurial
+	on top, and there's plenty more scope for head-scratching.
+	Most of these potential problems occur on the server side, not
+	the client side.  The good news is that once you've gotten a
+	configuration working, it will usually continue to work
+	indefinitely.</para>
+
+      <para>Before you try using Mercurial to talk to an ssh server,
+	it's best to make sure that you can use the normal
+	<command>ssh</command> or <command>putty</command> command to
+	talk to the server first.  If you run into problems with using
+	these commands directly, Mercurial surely won't work.  Worse,
+	it will obscure the underlying problem.  Any time you want to
+	debug ssh-related Mercurial problems, you should drop back to
+	making sure that plain ssh client commands work first,
+	<emphasis>before</emphasis> you worry about whether there's a
+	problem with Mercurial.</para>
+
+      <para>The first thing to be sure of on the server side is that
+	you can actually log in from another machine at all.  If you
+	can't use <command>ssh</command> or <command>putty</command>
+	to log in, the error message you get may give you a few hints
+	as to what's wrong.  The most common problems are as
+	follows.</para>
+      <itemizedlist>
+	<listitem><para>If you get a <quote>connection refused</quote>
+	    error, either there isn't an SSH daemon running on the
+	    server at all, or it's inaccessible due to firewall
+	    configuration.</para>
+	</listitem>
+	<listitem><para>If you get a <quote>no route to host</quote>
+	    error, you either have an incorrect address for the server
+	    or a seriously locked down firewall that won't admit its
+	    existence at all.</para>
+	</listitem>
+	<listitem><para>If you get a <quote>permission denied</quote>
+	    error, you may have mistyped the username on the server,
+	    or you could have mistyped your key's passphrase or the
+	    remote user's password.</para>
+	</listitem></itemizedlist>
+      <para>In summary, if you're having trouble talking to the
+	server's ssh daemon, first make sure that one is running at
+	all.  On many systems it will be installed, but disabled, by
+	default.  Once you're done with this step, you should then
+	check that the server's firewall is configured to allow
+	incoming connections on the port the ssh daemon is listening
+	on (usually 22).  Don't worry about more exotic possibilities
+	for misconfiguration until you've checked these two
+	first.</para>
+
+      <para>If you're using an authentication agent on the client side
+	to store passphrases for your keys, you ought to be able to
+	log into the server without being prompted for a passphrase or
+	a password.  If you're prompted for a passphrase, there are a
+	few possible culprits.</para>
+      <itemizedlist>
+	<listitem><para>You might have forgotten to use
+	    <command>ssh-add</command> or <command>pageant</command>
+	    to store the passphrase.</para>
+	</listitem>
+	<listitem><para>You might have stored the passphrase for the
+	    wrong key.</para>
+	</listitem></itemizedlist>
+      <para>If you're being prompted for the remote user's password,
+	there are another few possible problems to check.</para>
+      <itemizedlist>
+	<listitem><para>Either the user's home directory or their
+	    <filename role="special" class="directory">.ssh</filename>
+	    directory might have excessively liberal permissions.  As
+	    a result, the ssh daemon will not trust or read their
+	    <filename role="special">authorized_keys</filename> file.
+	    For example, a group-writable home or <filename
+	      role="special" class="directory">.ssh</filename>
+	    directory will often cause this symptom.</para>
+	</listitem>
+	<listitem><para>The user's <filename
+	      role="special">authorized_keys</filename> file may have
+	    a problem. If anyone other than the user owns or can write
+	    to that file, the ssh daemon will not trust or read
+	    it.</para>
+	</listitem></itemizedlist>
+
+      <para>In the ideal world, you should be able to run the
+	following command successfully, and it should print exactly
+	one line of output, the current date and time.</para>
+      <programlisting>ssh myserver date</programlisting>
+
+      <para>If, on your server, you have login scripts that print
+	banners or other junk even when running non-interactive
+	commands like this, you should fix them before you continue,
+	so that they only print output if they're run interactively.
+	Otherwise these banners will at least clutter up Mercurial's
+	output.  Worse, they could potentially cause problems with
+	running Mercurial commands remotely.  Mercurial makes tries to
+	detect and ignore banners in non-interactive
+	<command>ssh</command> sessions, but it is not foolproof.  (If
+	you're editing your login scripts on your server, the usual
+	way to see if a login script is running in an interactive
+	shell is to check the return code from the command
+	<literal>tty -s</literal>.)</para>
+
+      <para>Once you've verified that plain old ssh is working with
+	your server, the next step is to ensure that Mercurial runs on
+	the server.  The following command should run
+	successfully:</para>
+      <programlisting>ssh myserver hg version</programlisting>
+      <para>If you see an error message instead of normal <command
+	  role="hg-cmd">hg version</command> output, this is usually
+	because you haven't installed Mercurial to <filename
+	  class="directory">/usr/bin</filename>.  Don't worry if this
+	is the case; you don't need to do that.  But you should check
+	for a few possible problems.</para>
+      <itemizedlist>
+	<listitem><para>Is Mercurial really installed on the server at
+	    all?  I know this sounds trivial, but it's worth
+	    checking!</para>
+	</listitem>
+	<listitem><para>Maybe your shell's search path (usually set
+	    via the <envar>PATH</envar> environment variable) is
+	    simply misconfigured.</para>
+	</listitem>
+	<listitem><para>Perhaps your <envar>PATH</envar> environment
+	    variable is only being set to point to the location of the
+	    <command>hg</command> executable if the login session is
+	    interactive.  This can happen if you're setting the path
+	    in the wrong shell login script.  See your shell's
+	    documentation for details.</para>
+	</listitem>
+	<listitem><para>The <envar>PYTHONPATH</envar> environment
+	    variable may need to contain the path to the Mercurial
+	    Python modules.  It might not be set at all; it could be
+	    incorrect; or it may be set only if the login is
+	    interactive.</para>
+	</listitem></itemizedlist>
+
+      <para>If you can run <command role="hg-cmd">hg version</command>
+	over an ssh connection, well done! You've got the server and
+	client sorted out.  You should now be able to use Mercurial to
+	access repositories hosted by that username on that server.
+	If you run into problems with Mercurial and ssh at this point,
+	try using the <option role="hg-opt-global">--debug</option>
+	option to get a clearer picture of what's going on.</para>
+
+    </sect2>
+    <sect2>
+      <title>Using compression with ssh</title>
+
+      <para>Mercurial does not compress data when it uses the ssh
+	protocol, because the ssh protocol can transparently compress
+	data.  However, the default behaviour of ssh clients is
+	<emphasis>not</emphasis> to request compression.</para>
+
+      <para>Over any network other than a fast LAN (even a wireless
+	network), using compression is likely to significantly speed
+	up Mercurial's network operations.  For example, over a WAN,
+	someone measured compression as reducing the amount of time
+	required to clone a particularly large repository from 51
+	minutes to 17 minutes.</para>
+
+      <para>Both <command>ssh</command> and <command>plink</command>
+	accept a <option role="cmd-opt-ssh">-C</option> option which
+	turns on compression.  You can easily edit your <filename
+	  role="special"> /.hgrc</filename>\ to enable compression for
+	all of Mercurial's uses of the ssh protocol.</para>
+      <programlisting>[ui] ssh = ssh -C</programlisting>
+
+      <para>If you use <command>ssh</command>, you can configure it to
+	always use compression when talking to your server.  To do
+	this, edit your <filename
+	  role="special">.ssh/config</filename> file (which may not
+	yet exist), as follows.</para>
+      <programlisting>Host hg Compression yes HostName
+	hg.example.com</programlisting>
+      <para>This defines an alias, <literal>hg</literal>.  When you
+	use it on the <command>ssh</command> command line or in a
+	Mercurial <literal>ssh</literal>-protocol URL, it will cause
+	<command>ssh</command> to connect to
+	<literal>hg.example.com</literal> and use compression.  This
+	gives you both a shorter name to type and compression, each of
+	which is a good thing in its own right.</para>
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:collab:cgi">
+    <title>Serving over HTTP using CGI</title>
+
+    <para>Depending on how ambitious you are, configuring Mercurial's
+      CGI interface can take anything from a few moments to several
+      hours.</para>
+
+    <para>We'll begin with the simplest of examples, and work our way
+      towards a more complex configuration.  Even for the most basic
+      case, you're almost certainly going to need to read and modify
+      your web server's configuration.</para>
+
+    <note>
+      <para>  Configuring a web server is a complex, fiddly, and
+	highly system-dependent activity.  I can't possibly give you
+	instructions that will cover anything like all of the cases
+	you will encounter. Please use your discretion and judgment in
+	following the sections below.  Be prepared to make plenty of
+	mistakes, and to spend a lot of time reading your server's
+	error logs.</para>
+    </note>
+
+    <sect2>
+      <title>Web server configuration checklist</title>
+
+      <para>Before you continue, do take a few moments to check a few
+	aspects of your system's setup.</para>
+
+      <orderedlist>
+	<listitem><para>Do you have a web server installed at all?
+	    Mac OS X ships with Apache, but many other systems may not
+	    have a web server installed.</para>
+	</listitem>
+	<listitem><para>If you have a web server installed, is it
+	    actually running?  On most systems, even if one is
+	    present, it will be disabled by default.</para>
+	</listitem>
+	<listitem><para>Is your server configured to allow you to run
+	    CGI programs in the directory where you plan to do so?
+	    Most servers default to explicitly disabling the ability
+	    to run CGI programs.</para>
+	</listitem></orderedlist>
+
+      <para>If you don't have a web server installed, and don't have
+	substantial experience configuring Apache, you should consider
+	using the <literal>lighttpd</literal> web server instead of
+	Apache.  Apache has a well-deserved reputation for baroque and
+	confusing configuration. While <literal>lighttpd</literal> is
+	less capable in some ways than Apache, most of these
+	capabilities are not relevant to serving Mercurial
+	repositories.  And <literal>lighttpd</literal> is undeniably
+	<emphasis>much</emphasis> easier to get started with than
+	Apache.</para>
+
+    </sect2>
+    <sect2>
+      <title>Basic CGI configuration</title>
+
+      <para>On Unix-like systems, it's common for users to have a
+	subdirectory named something like <filename
+	  class="directory">public_html</filename> in their home
+	directory, from which they can serve up web pages.  A file
+	named <filename>foo</filename> in this directory will be
+	accessible at a URL of the form
+	<literal>http://www.example.com/\
+	  {</literal>username/foo}.</para>
+
+      <para>To get started, find the <filename
+	  role="special">hgweb.cgi</filename> script that should be
+	present in your Mercurial installation.  If you can't quickly
+	find a local copy on your system, simply download one from the
+	master Mercurial repository at <ulink
+	  url="http://www.selenic.com/repo/hg/raw-file/tip/hgweb.cgi">http://www.selenic.com/repo/hg/raw-file/tip/hgweb.cgi</ulink>.</para>
+
+      <para>You'll need to copy this script into your <filename
+	  class="directory">public_html</filename> directory, and
+	ensure that it's executable.</para>
+      <programlisting>cp .../hgweb.cgi ~/public_html chmod 755
+	~/public_html/hgweb.cgi</programlisting>
+      <para>The <literal>755</literal> argument to
+	<command>chmod</command> is a little more general than just
+	making the script executable: it ensures that the script is
+	executable by anyone, and that <quote>group</quote> and
+	<quote>other</quote> write permissions are
+	<emphasis>not</emphasis> set.  If you were to leave those
+	write permissions enabled, Apache's <literal>suexec</literal>
+	subsystem would likely refuse to execute the script.  In fact,
+	<literal>suexec</literal> also insists that the
+	<emphasis>directory</emphasis> in which the script resides
+	must not be writable by others.</para>
+      <programlisting>chmod 755 ~/public_html</programlisting>
+
+      <sect3 id="sec:collab:wtf">
+	<title>What could <emphasis>possibly</emphasis> go
+	  wrong?</title>
+
+	<para>Once you've copied the CGI script into place, go into a
+	  web browser, and try to open the URL <ulink
+	    url="http://myhostname/
+	    myuser/hgweb.cgi">http://myhostname/
+	    myuser/hgweb.cgi</ulink>, <emphasis>but</emphasis> brace
+	  yourself for instant failure.  There's a high probability
+	  that trying to visit this URL will fail, and there are many
+	  possible reasons for this.  In fact, you're likely to
+	  stumble over almost every one of the possible errors below,
+	  so please read carefully.  The following are all of the
+	  problems I ran into on a system running Fedora 7, with a
+	  fresh installation of Apache, and a user account that I
+	  created specially to perform this exercise.</para>
+
+	<para>Your web server may have per-user directories disabled.
+	  If you're using Apache, search your config file for a
+	  <literal>UserDir</literal> directive.  If there's none
+	  present, per-user directories will be disabled.  If one
+	  exists, but its value is <literal>disabled</literal>, then
+	  per-user directories will be disabled.  Otherwise, the
+	  string after <literal>UserDir</literal> gives the name of
+	  the subdirectory that Apache will look in under your home
+	  directory, for example <filename
+	    class="directory">public_html</filename>.</para>
+
+	<para>Your file access permissions may be too restrictive.
+	  The web server must be able to traverse your home directory
+	  and directories under your <filename
+	    class="directory">public_html</filename> directory, and
+	  read files under the latter too.  Here's a quick recipe to
+	  help you to make your permissions more appropriate.</para>
+	<programlisting>chmod 755 ~ find ~/public_html -type d -print0
+	  | xargs -0r chmod 755 find ~/public_html -type f -print0 |
+	  xargs -0r chmod 644</programlisting>
+
+	<para>The other possibility with permissions is that you might
+	  get a completely empty window when you try to load the
+	  script.  In this case, it's likely that your access
+	  permissions are \emph{too permissive}.  Apache's
+	  <literal>suexec</literal> subsystem won't execute a script
+	  that's group- or world-writable, for example.</para>
+
+	<para>Your web server may be configured to disallow execution
+	  of CGI programs in your per-user web directory.  Here's
+	  Apache's default per-user configuration from my Fedora
+	  system.</para>
+	<programlisting>&lt;Directory /home/*/public_html&gt;
+	  AllowOverride FileInfo AuthConfig Limit Options MultiViews
+	  Indexes SymLinksIfOwnerMatch IncludesNoExec &lt;Limit GET
+	  POST OPTIONS&gt; Order allow,deny Allow from all
+	  &lt;/Limit&gt; &lt;LimitExcept GET POST OPTIONS&gt; Order
+	  deny,allow Deny from all &lt;/LimitExcept&gt;
+	  &lt;/Directory&gt;</programlisting>
+	<para>If you find a similar-looking
+	  <literal>Directory</literal> group in your Apache
+	  configuration, the directive to look at inside it is
+	  <literal>Options</literal>. Add <literal>ExecCGI</literal>
+	  to the end of this list if it's missing, and restart the web
+	  server.</para>
+
+	<para>If you find that Apache serves you the text of the CGI
+	  script instead of executing it, you may need to either
+	  uncomment (if already present) or add a directive like
+	  this.</para>
+	<programlisting>AddHandler cgi-script .cgi</programlisting>
+
+	<para>The next possibility is that you might be served with a
+	  colourful Python backtrace claiming that it can't import a
+	  <literal>mercurial</literal>-related module.  This is
+	  actually progress!  The server is now capable of executing
+	  your CGI script.  This error is only likely to occur if
+	  you're running a private installation of Mercurial, instead
+	  of a system-wide version.  Remember that the web server runs
+	  the CGI program without any of the environment variables
+	  that you take for granted in an interactive session.  If
+	  this error happens to you, edit your copy of <filename
+	    role="special">hgweb.cgi</filename> and follow the
+	  directions inside it to correctly set your
+	  <envar>PYTHONPATH</envar> environment variable.</para>
+
+	<para>Finally, you are <emphasis>certain</emphasis> to by
+	  served with another colourful Python backtrace: this one
+	  will complain that it can't find <filename
+	    class="directory">/path/to/repository</filename>.  Edit
+	  your <filename role="special">hgweb.cgi</filename> script
+	  and replace the <filename
+	    class="directory">/path/to/repository</filename> string
+	  with the complete path to the repository you want to serve
+	  up.</para>
+
+	<para>At this point, when you try to reload the page, you
+	  should be presented with a nice HTML view of your
+	  repository's history.  Whew!</para>
+
+      </sect3>
+      <sect3>
+	<title>Configuring lighttpd</title>
+
+	<para>To be exhaustive in my experiments, I tried configuring
+	  the increasingly popular <literal>lighttpd</literal> web
+	  server to serve the same repository as I described with
+	  Apache above.  I had already overcome all of the problems I
+	  outlined with Apache, many of which are not server-specific.
+	  As a result, I was fairly sure that my file and directory
+	  permissions were good, and that my <filename
+	    role="special">hgweb.cgi</filename> script was properly
+	  edited.</para>
+
+	<para>Once I had Apache running, getting
+	  <literal>lighttpd</literal> to serve the repository was a
+	  snap (in other words, even if you're trying to use
+	  <literal>lighttpd</literal>, you should read the Apache
+	  section).  I first had to edit the
+	  <literal>mod_access</literal> section of its config file to
+	  enable <literal>mod_cgi</literal> and
+	  <literal>mod_userdir</literal>, both of which were disabled
+	  by default on my system.  I then added a few lines to the
+	  end of the config file, to configure these modules.</para>
+	<programlisting>userdir.path = "public_html" cgi.assign = (
+	  ".cgi" =&gt; "" )</programlisting>
+	<para>With this done, <literal>lighttpd</literal> ran
+	  immediately for me.  If I had configured
+	  <literal>lighttpd</literal> before Apache, I'd almost
+	  certainly have run into many of the same system-level
+	  configuration problems as I did with Apache.  However, I
+	  found <literal>lighttpd</literal> to be noticeably easier to
+	  configure than Apache, even though I've used Apache for over
+	  a decade, and this was my first exposure to
+	  <literal>lighttpd</literal>.</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Sharing multiple repositories with one CGI script</title>
+
+      <para>The <filename role="special">hgweb.cgi</filename> script
+	only lets you publish a single repository, which is an
+	annoying restriction.  If you want to publish more than one
+	without wracking yourself with multiple copies of the same
+	script, each with different names, a better choice is to use
+	the <filename role="special">hgwebdir.cgi</filename>
+	script.</para>
+
+      <para>The procedure to configure <filename
+	  role="special">hgwebdir.cgi</filename> is only a little more
+	involved than for <filename
+	  role="special">hgweb.cgi</filename>.  First, you must obtain
+	a copy of the script.  If you don't have one handy, you can
+	download a copy from the master Mercurial repository at <ulink
+	  url="http://www.selenic.com/repo/hg/raw-file/tip/hgwebdir.cgi">http://www.selenic.com/repo/hg/raw-file/tip/hgwebdir.cgi</ulink>.</para>
+
+      <para>You'll need to copy this script into your <filename
+	  class="directory">public_html</filename> directory, and
+	ensure that it's executable.</para>
+      <programlisting>cp .../hgwebdir.cgi ~/public_html chmod 755
+	~/public_html ~/public_html/hgwebdir.cgi</programlisting>
+      <para>With basic configuration out of the way, try to visit
+	<ulink url="http://myhostname/
+	  myuser/hgwebdir.cgi">http://myhostname/
+	  myuser/hgwebdir.cgi</ulink> in your browser.  It should
+	display an empty list of repositories.  If you get a blank
+	window or error message, try walking through the list of
+	potential problems in section <xref
+	  linkend="sec:collab:wtf"/>.</para>
+
+      <para>The <filename role="special">hgwebdir.cgi</filename>
+	script relies on an external configuration file.  By default,
+	it searches for a file named <filename
+	  role="special">hgweb.config</filename> in the same directory
+	as itself.  You'll need to create this file, and make it
+	world-readable.  The format of the file is similar to a
+	Windows <quote>ini</quote> file, as understood by Python's
+	<literal>ConfigParser</literal>
+	<citation>web:configparser</citation> module.</para>
+
+      <para>The easiest way to configure <filename
+	  role="special">hgwebdir.cgi</filename> is with a section
+	named <literal>collections</literal>.  This will automatically
+	publish <emphasis>every</emphasis> repository under the
+	directories you name.  The section should look like
+	this:</para>
+      <programlisting>[collections] /my/root =
+	/my/root</programlisting>
+      <para>Mercurial interprets this by looking at the directory name
+	on the <emphasis>right</emphasis> hand side of the
+	<quote><literal>=</literal></quote> sign; finding repositories
+	in that directory hierarchy; and using the text on the
+	<emphasis>left</emphasis> to strip off matching text from the
+	names it will actually list in the web interface.  The
+	remaining component of a path after this stripping has
+	occurred is called a <quote>virtual path</quote>.</para>
+
+      <para>Given the example above, if we have a repository whose
+	local path is <filename
+	  class="directory">/my/root/this/repo</filename>, the CGI
+	script will strip the leading <filename
+	  class="directory">/my/root</filename> from the name, and
+	publish the repository with a virtual path of <filename
+	  class="directory">this/repo</filename>.  If the base URL for
+	our CGI script is <ulink url="http://myhostname/
+	  myuser/hgwebdir.cgi">http://myhostname/
+	  myuser/hgwebdir.cgi</ulink>, the complete URL for that
+	repository will be <ulink url="http://myhostname/
+	  myuser/hgwebdir.cgi/this/repo">http://myhostname/
+	  myuser/hgwebdir.cgi/this/repo</ulink>.</para>
+
+      <para>If we replace <filename
+	  class="directory">/my/root</filename> on the left hand side
+	of this example with <filename
+	  class="directory">/my</filename>, then <filename
+	  role="special">hgwebdir.cgi</filename> will only strip off
+	<filename class="directory">/my</filename> from the repository
+	name, and will give us a virtual path of <filename
+	  class="directory">root/this/repo</filename> instead of
+	<filename class="directory">this/repo</filename>.</para>
+
+      <para>The <filename role="special">hgwebdir.cgi</filename>
+	script will recursively search each directory listed in the
+	<literal>collections</literal> section of its configuration
+	file, but it will <literal>not</literal> recurse into the
+	repositories it finds.</para>
+
+      <para>The <literal>collections</literal> mechanism makes it easy
+	to publish many repositories in a <quote>fire and
+	  forget</quote> manner.  You only need to set up the CGI
+	script and configuration file one time.  Afterwards, you can
+	publish or unpublish a repository at any time by simply moving
+	it into, or out of, the directory hierarchy in which you've
+	configured <filename role="special">hgwebdir.cgi</filename> to
+	look.</para>
+
+      <sect3>
+	<title>Explicitly specifying which repositories to
+	  publish</title>
+
+	<para>In addition to the <literal>collections</literal>
+	  mechanism, the <filename
+	    role="special">hgwebdir.cgi</filename> script allows you
+	  to publish a specific list of repositories.  To do so,
+	  create a <literal>paths</literal> section, with contents of
+	  the following form.</para>
+	<programlisting>[paths] repo1 = /my/path/to/some/repo repo2 =
+	  /some/path/to/another</programlisting>
+	<para>In this case, the virtual path (the component that will
+	  appear in a URL) is on the left hand side of each
+	  definition, while the path to the repository is on the
+	  right.  Notice that there does not need to be any
+	  relationship between the virtual path you choose and the
+	  location of a repository in your filesystem.</para>
+
+	<para>If you wish, you can use both the
+	  <literal>collections</literal> and <literal>paths</literal>
+	  mechanisms simultaneously in a single configuration
+	  file.</para>
+
+	<note>
+	  <para>  If multiple repositories have the same virtual path,
+	    <filename role="special">hgwebdir.cgi</filename> will not
+	    report an error.  Instead, it will behave
+	    unpredictably.</para>
+	</note>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Downloading source archives</title>
+
+      <para>Mercurial's web interface lets users download an archive
+	of any revision.  This archive will contain a snapshot of the
+	working directory as of that revision, but it will not contain
+	a copy of the repository data.</para>
+
+      <para>By default, this feature is not enabled.  To enable it,
+	you'll need to add an <envar
+	  role="rc-item-web">allow_archive</envar> item to the
+	<literal role="rc-web">web</literal> section of your <filename
+	  role="special"> /.hgrc</filename>.</para>
+
+    </sect2>
+    <sect2>
+      <title>Web configuration options</title>
+
+      <para>Mercurial's web interfaces (the <command role="hg-cmd">hg
+	  serve</command> command, and the <filename
+	  role="special">hgweb.cgi</filename> and <filename
+	  role="special">hgwebdir.cgi</filename> scripts) have a
+	number of configuration options that you can set.  These
+	belong in a section named <literal
+	  role="rc-web">web</literal>.</para>
+      <itemizedlist>
+	<listitem><para><envar
+	      role="rc-item-web">allow_archive</envar>: Determines
+	    which (if any) archive download mechanisms Mercurial
+	    supports.  If you enable this feature, users of the web
+	    interface will be able to download an archive of whatever
+	    revision of a repository they are viewing. To enable the
+	    archive feature, this item must take the form of a
+	    sequence of words drawn from the list below.</para>
+	  <itemizedlist>
+	    <listitem><para><literal>bz2</literal>: A
+		<command>tar</command> archive, compressed using
+		<literal>bzip2</literal> compression.  This has the
+		best compression ratio, but uses the most CPU time on
+		the server.</para>
+	    </listitem>
+	    <listitem><para><literal>gz</literal>: A
+		<command>tar</command> archive, compressed using
+		<literal>gzip</literal> compression.</para>
+	    </listitem>
+	    <listitem><para><literal>zip</literal>: A
+		<command>zip</command> archive, compressed using LZW
+		compression.  This format has the worst compression
+		ratio, but is widely used in the Windows world.</para>
+	    </listitem>
+	  </itemizedlist>
+	  <para>  If you provide an empty list, or don't have an
+	    <envar role="rc-item-web">allow_archive</envar> entry at
+	    all, this feature will be disabled.  Here is an example of
+	    how to enable all three supported formats.</para>
+	  <programlisting>[web] allow_archive = bz2 gz
+	    zip</programlisting>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">allowpull</envar>:
+	    Boolean.  Determines whether the web interface allows
+	    remote users to <command role="hg-cmd">hg pull</command>
+	    and <command role="hg-cmd">hg clone</command> this
+	    repository over HTTP.  If set to <literal>no</literal> or
+	    <literal>false</literal>, only the
+	    <quote>human-oriented</quote> portion of the web interface
+	    is available.</para>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">contact</envar>:
+	    String.  A free-form (but preferably brief) string
+	    identifying the person or group in charge of the
+	    repository.  This often contains the name and email
+	    address of a person or mailing list.  It often makes sense
+	    to place this entry in a repository's own <filename
+	      role="special">.hg/hgrc</filename> file, but it can make
+	    sense to use in a global <filename role="special">
+	      /.hgrc</filename>\ if every repository has a single
+	    maintainer.</para>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">maxchanges</envar>:
+	    Integer.  The default maximum number of changesets to
+	    display in a single page of output.</para>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">maxfiles</envar>:
+	    Integer.  The default maximum number of modified files to
+	    display in a single page of output.</para>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">stripes</envar>:
+	    Integer.  If the web interface displays alternating
+	    <quote>stripes</quote> to make it easier to visually align
+	    rows when you are looking at a table, this number controls
+	    the number of rows in each stripe.</para>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">style</envar>:
+	    Controls the template Mercurial uses to display the web
+	    interface.  Mercurial ships with two web templates, named
+	    <literal>default</literal> and <literal>gitweb</literal>
+	    (the latter is much more visually attractive).  You can
+	    also specify a custom template of your own; see chapter
+	    <xref linkend="chap:template"/> for details.
+	    Here, you can see how to enable the
+	    <literal>gitweb</literal> style.</para>
+	  <programlisting>[web] style = gitweb</programlisting>
+	</listitem>
+	<listitem><para><envar role="rc-item-web">templates</envar>:
+	    Path.  The directory in which to search for template
+	    files.  By default, Mercurial searches in the directory in
+	    which it was installed.</para>
+	</listitem></itemizedlist>
+      <para>If you are using <filename
+	  role="special">hgwebdir.cgi</filename>, you can place a few
+	configuration items in a <literal role="rc-web">web</literal>
+	section of the <filename
+	  role="special">hgweb.config</filename> file instead of a
+	<filename role="special"> /.hgrc</filename>\ file, for
+	convenience.  These items are <envar
+	  role="rc-item-web">motd</envar> and <envar
+	  role="rc-item-web">style</envar>.</para>
+
+      <sect3>
+	<title>Options specific to an individual repository</title>
+
+	<para>A few <literal role="rc-web">web</literal> configuration
+	  items ought to be placed in a repository's local <filename
+	    role="special">.hg/hgrc</filename>, rather than a user's
+	  or global <filename role="special">
+	    /.hgrc</filename>.</para>
+	<itemizedlist>
+	  <listitem><para><envar
+		role="rc-item-web">description</envar>: String.  A
+	      free-form (but preferably brief) string that describes
+	      the contents or purpose of the repository.</para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-web">name</envar>:
+	      String.  The name to use for the repository in the web
+	      interface.  This overrides the default name, which is
+	      the last component of the repository's path.</para>
+	  </listitem></itemizedlist>
+
+      </sect3>
+      <sect3>
+	<title>Options specific to the <command role="hg-cmd">hg
+	    serve</command> command</title>
+
+	<para>Some of the items in the <literal
+	    role="rc-web">web</literal> section of a <filename
+	    role="special"> /.hgrc</filename>\ file are only for use
+	  with the <command role="hg-cmd">hg serve</command>
+	  command.</para>
+	<itemizedlist>
+	  <listitem><para><envar role="rc-item-web">accesslog</envar>:
+	      Path.  The name of a file into which to write an access
+	      log.  By default, the <command role="hg-cmd">hg
+		serve</command> command writes this information to
+	      standard output, not to a file.  Log entries are written
+	      in the standard <quote>combined</quote> file format used
+	      by almost all web servers.</para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-web">address</envar>:
+	      String.  The local address on which the server should
+	      listen for incoming connections.  By default, the server
+	      listens on all addresses.</para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-web">errorlog</envar>:
+	      Path.  The name of a file into which to write an error
+	      log.  By default, the <command role="hg-cmd">hg
+		serve</command> command writes this information to
+	      standard error, not to a file.</para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-web">ipv6</envar>:
+	      Boolean.  Whether to use the IPv6 protocol. By default,
+	      IPv6 is not used.</para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-web">port</envar>:
+	      Integer.  The TCP port number on which the server should
+	      listen.  The default port number used is 8000.</para>
+	  </listitem></itemizedlist>
+
+      </sect3>
+      <sect3>
+	<title>Choosing the right <filename role="special">
+	    /.hgrc</filename>\ file to add <literal
+	    role="rc-web">web</literal> items to</title>
+
+	<para>It is important to remember that a web server like
+	  Apache or <literal>lighttpd</literal> will run under a user
+	  ID that is different to yours. CGI scripts run by your
+	  server, such as <filename
+	    role="special">hgweb.cgi</filename>, will usually also run
+	  under that user ID.</para>
+
+	<para>If you add <literal role="rc-web">web</literal> items to
+	  your own personal <filename role="special">
+	    /.hgrc</filename>\ file, CGI scripts won't read that
+	  <filename role="special"> /.hgrc</filename>\ file.  Those
+	  settings will thus only affect the behaviour of the <command
+	    role="hg-cmd">hg serve</command> command when you run it.
+	  To cause CGI scripts to see your settings, either create a
+	  <filename role="special"> /.hgrc</filename>\ file in the
+	  home directory of the user ID that runs your web server, or
+	  add those settings to a system-wide <filename
+	    role="special"> /.hgrc</filename>\ file.</para>
+
+
+      </sect3>
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch07-filenames.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch07-filenames.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,392 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:names">
+  <title>File names and pattern matching</title>
+
+  <para>Mercurial provides mechanisms that let you work with file
+    names in a consistent and expressive way.</para>
+
+  <sect1>
+    <title>Simple file naming</title>
+
+    <para>Mercurial uses a unified piece of machinery <quote>under the
+	hood</quote> to handle file names.  Every command behaves
+      uniformly with respect to file names.  The way in which commands
+      work with file names is as follows.</para>
+
+    <para>If you explicitly name real files on the command line,
+      Mercurial works with exactly those files, as you would expect.
+      <!-- &interaction.filenames.files; --></para>
+
+    <para>When you provide a directory name, Mercurial will interpret
+      this as <quote>operate on every file in this directory and its
+	subdirectories</quote>. Mercurial traverses the files and
+      subdirectories in a directory in alphabetical order.  When it
+      encounters a subdirectory, it will traverse that subdirectory
+      before continuing with the current directory. <!--
+      &interaction.filenames.dirs; --></para>
+
+  </sect1>
+  <sect1>
+    <title>Running commands without any file names</title>
+
+    <para>Mercurial's commands that work with file names have useful
+      default behaviours when you invoke them without providing any
+      file names or patterns.  What kind of behaviour you should
+      expect depends on what the command does.  Here are a few rules
+      of thumb you can use to predict what a command is likely to do
+      if you don't give it any names to work with.</para>
+    <itemizedlist>
+      <listitem><para>Most commands will operate on the entire working
+	  directory. This is what the <command role="hg-cmd">hg
+	    add</command> command does, for example.</para>
+      </listitem>
+      <listitem><para>If the command has effects that are difficult or
+	  impossible to reverse, it will force you to explicitly
+	  provide at least one name or pattern (see below).  This
+	  protects you from accidentally deleting files by running
+	  <command role="hg-cmd">hg remove</command> with no
+	  arguments, for example.</para>
+      </listitem></itemizedlist>
+
+    <para>It's easy to work around these default behaviours if they
+      don't suit you.  If a command normally operates on the whole
+      working directory, you can invoke it on just the current
+      directory and its subdirectories by giving it the name
+      <quote><filename class="directory">.</filename></quote>. <!--
+      &interaction.filenames.wdir-subdir; --></para>
+
+    <para>Along the same lines, some commands normally print file
+      names relative to the root of the repository, even if you're
+      invoking them from a subdirectory.  Such a command will print
+      file names relative to your subdirectory if you give it explicit
+      names.  Here, we're going to run <command role="hg-cmd">hg
+	status</command> from a subdirectory, and get it to operate on
+      the entire working directory while printing file names relative
+      to our subdirectory, by passing it the output of the <command
+	role="hg-cmd">hg root</command> command. <!--
+      &interaction.filenames.wdir-relname; --></para>
+
+  </sect1>
+  <sect1>
+    <title>Telling you what's going on</title>
+
+    <para>The <command role="hg-cmd">hg add</command> example in the
+      preceding section illustrates something else that's helpful
+      about Mercurial commands.  If a command operates on a file that
+      you didn't name explicitly on the command line, it will usually
+      print the name of the file, so that you will not be surprised
+      what's going on.</para>
+
+    <para>The principle here is of <emphasis>least
+	surprise</emphasis>.  If you've exactly named a file on the
+      command line, there's no point in repeating it back at you.  If
+      Mercurial is acting on a file <emphasis>implicitly</emphasis>,
+      because you provided no names, or a directory, or a pattern (see
+      below), it's safest to tell you what it's doing.</para>
+
+    <para>For commands that behave this way, you can silence them
+      using the <option role="hg-opt-global">-q</option> option.  You
+      can also get them to print the name of every file, even those
+      you've named explicitly, using the <option
+	role="hg-opt-global">-v</option> option.</para>
+
+  </sect1>
+  <sect1>
+    <title>Using patterns to identify files</title>
+
+    <para>In addition to working with file and directory names,
+      Mercurial lets you use <emphasis>patterns</emphasis> to identify
+      files.  Mercurial's pattern handling is expressive.</para>
+
+    <para>On Unix-like systems (Linux, MacOS, etc.), the job of
+      matching file names to patterns normally falls to the shell.  On
+      these systems, you must explicitly tell Mercurial that a name is
+      a pattern.  On Windows, the shell does not expand patterns, so
+      Mercurial will automatically identify names that are patterns,
+      and expand them for you.</para>
+
+    <para>To provide a pattern in place of a regular name on the
+      command line, the mechanism is simple:</para>
+    <programlisting>syntax:patternbody</programlisting>
+    <para>That is, a pattern is identified by a short text string that
+      says what kind of pattern this is, followed by a colon, followed
+      by the actual pattern.</para>
+
+    <para>Mercurial supports two kinds of pattern syntax.  The most
+      frequently used is called <literal>glob</literal>; this is the
+      same kind of pattern matching used by the Unix shell, and should
+      be familiar to Windows command prompt users, too.</para>
+
+    <para>When Mercurial does automatic pattern matching on Windows,
+      it uses <literal>glob</literal> syntax.  You can thus omit the
+      <quote><literal>glob:</literal></quote> prefix on Windows, but
+      it's safe to use it, too.</para>
+
+    <para>The <literal>re</literal> syntax is more powerful; it lets
+      you specify patterns using regular expressions, also known as
+      regexps.</para>
+
+    <para>By the way, in the examples that follow, notice that I'm
+      careful to wrap all of my patterns in quote characters, so that
+      they won't get expanded by the shell before Mercurial sees
+      them.</para>
+
+    <sect2>
+      <title>Shell-style <literal>glob</literal> patterns</title>
+
+      <para>This is an overview of the kinds of patterns you can use
+	when you're matching on glob patterns.</para>
+
+      <para>The <quote><literal>*</literal></quote> character matches
+	any string, within a single directory. <!--
+	&interaction.filenames.glob.star; --></para>
+
+      <para>The <quote><literal>**</literal></quote> pattern matches
+	any string, and crosses directory boundaries.  It's not a
+	standard Unix glob token, but it's accepted by several popular
+	Unix shells, and is very useful. <!--
+	&interaction.filenames.glob.starstar; --></para>
+
+      <para>The <quote><literal>?</literal></quote> pattern matches
+	any single character. <!--
+	&interaction.filenames.glob.question; --></para>
+
+      <para>The <quote><literal>[</literal></quote> character begins a
+	<emphasis>character class</emphasis>.  This matches any single
+	character within the class.  The class ends with a
+	<quote><literal>]</literal></quote> character.  A class may
+	contain multiple <emphasis>range</emphasis>s of the form
+	<quote><literal>a-f</literal></quote>, which is shorthand for
+	<quote><literal>abcdef</literal></quote>. <!--
+	&interaction.filenames.glob.range; --> If the first character
+	after the <quote><literal>[</literal></quote> in a character
+	class is a <quote><literal>!</literal></quote>, it
+	<emphasis>negates</emphasis> the class, making it match any
+	single character not in the class.</para>
+
+      <para>A <quote><literal>{</literal></quote> begins a group of
+	subpatterns, where the whole group matches if any subpattern
+	in the group matches.  The <quote><literal>,</literal></quote>
+	character separates subpatterns, and <quote>\texttt{}}</quote>
+	ends the group. <!-- &interaction.filenames.glob.group;
+	--></para>
+
+      <sect3>
+	<title>Watch out!</title>
+
+	<para>Don't forget that if you want to match a pattern in any
+	  directory, you should not be using the
+	  <quote><literal>*</literal></quote> match-any token, as this
+	  will only match within one directory.  Instead, use the
+	  <quote><literal>**</literal></quote> token.  This small
+	  example illustrates the difference between the two. <!--
+	  &interaction.filenames.glob.star-starstar; --></para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Regular expression matching with <literal>re</literal>
+	patterns</title>
+
+      <para>Mercurial accepts the same regular expression syntax as
+	the Python programming language (it uses Python's regexp
+	engine internally). This is based on the Perl language's
+	regexp syntax, which is the most popular dialect in use (it's
+	also used in Java, for example).</para>
+
+      <para>I won't discuss Mercurial's regexp dialect in any detail
+	here, as regexps are not often used.  Perl-style regexps are
+	in any case already exhaustively documented on a multitude of
+	web sites, and in many books.  Instead, I will focus here on a
+	few things you should know if you find yourself needing to use
+	regexps with Mercurial.</para>
+
+      <para>A regexp is matched against an entire file name, relative
+	to the root of the repository.  In other words, even if you're
+	already in subbdirectory <filename
+	  class="directory">foo</filename>, if you want to match files
+	under this directory, your pattern must start with
+	<quote><literal>foo/</literal></quote>.</para>
+
+      <para>One thing to note, if you're familiar with Perl-style
+	regexps, is that Mercurial's are <emphasis>rooted</emphasis>.
+	That is, a regexp starts matching against the beginning of a
+	string; it doesn't look for a match anywhere within the
+	string.  To match anywhere in a string, start your pattern
+	with <quote><literal>.*</literal></quote>.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Filtering files</title>
+
+    <para>Not only does Mercurial give you a variety of ways to
+      specify files; it lets you further winnow those files using
+      <emphasis>filters</emphasis>.  Commands that work with file
+      names accept two filtering options.</para>
+    <itemizedlist>
+      <listitem><para><option role="hg-opt-global">-I</option>, or
+	  <option role="hg-opt-global">--include</option>, lets you
+	  specify a pattern that file names must match in order to be
+	  processed.</para>
+      </listitem>
+      <listitem><para><option role="hg-opt-global">-X</option>, or
+	  <option role="hg-opt-global">--exclude</option>, gives you a
+	  way to <emphasis>avoid</emphasis> processing files, if they
+	  match this pattern.</para>
+      </listitem></itemizedlist>
+    <para>You can provide multiple <option
+	role="hg-opt-global">-I</option> and <option
+	role="hg-opt-global">-X</option> options on the command line,
+      and intermix them as you please.  Mercurial interprets the
+      patterns you provide using glob syntax by default (but you can
+      use regexps if you need to).</para>
+
+    <para>You can read a <option role="hg-opt-global">-I</option>
+      filter as <quote>process only the files that match this
+	filter</quote>. <!-- &interaction.filenames.filter.include;
+      --> The <option role="hg-opt-global">-X</option> filter is best
+      read as <quote>process only the files that don't match this
+	pattern</quote>. <!-- &interaction.filenames.filter.exclude;
+      --></para>
+
+  </sect1>
+  <sect1>
+    <title>Ignoring unwanted files and directories</title>
+
+    <para>XXX.</para>
+
+  </sect1>
+  <sect1 id="sec:names:case">
+    <title>Case sensitivity</title>
+
+    <para>If you're working in a mixed development environment that
+      contains both Linux (or other Unix) systems and Macs or Windows
+      systems, you should keep in the back of your mind the knowledge
+      that they treat the case (<quote>N</quote> versus
+      <quote>n</quote>) of file names in incompatible ways.  This is
+      not very likely to affect you, and it's easy to deal with if it
+      does, but it could surprise you if you don't know about
+      it.</para>
+
+    <para>Operating systems and filesystems differ in the way they
+      handle the <emphasis>case</emphasis> of characters in file and
+      directory names.  There are three common ways to handle case in
+      names.</para>
+    <itemizedlist>
+      <listitem><para>Completely case insensitive.  Uppercase and
+	  lowercase versions of a letter are treated as identical,
+	  both when creating a file and during subsequent accesses.
+	  This is common on older DOS-based systems.</para>
+      </listitem>
+      <listitem><para>Case preserving, but insensitive.  When a file
+	  or directory is created, the case of its name is stored, and
+	  can be retrieved and displayed by the operating system.
+	  When an existing file is being looked up, its case is
+	  ignored.  This is the standard arrangement on Windows and
+	  MacOS.  The names <filename>foo</filename> and
+	  <filename>FoO</filename> identify the same file.  This
+	  treatment of uppercase and lowercase letters as
+	  interchangeable is also referred to as <emphasis>case
+	    folding</emphasis>.</para>
+      </listitem>
+      <listitem><para>Case sensitive.  The case of a name is
+	  significant at all times. The names <filename>foo</filename>
+	  and {FoO} identify different files.  This is the way Linux
+	  and Unix systems normally work.</para>
+      </listitem></itemizedlist>
+
+    <para>On Unix-like systems, it is possible to have any or all of
+      the above ways of handling case in action at once.  For example,
+      if you use a USB thumb drive formatted with a FAT32 filesystem
+      on a Linux system, Linux will handle names on that filesystem in
+      a case preserving, but insensitive, way.</para>
+
+    <sect2>
+      <title>Safe, portable repository storage</title>
+
+      <para>Mercurial's repository storage mechanism is <emphasis>case
+	  safe</emphasis>.  It translates file names so that they can
+	be safely stored on both case sensitive and case insensitive
+	filesystems.  This means that you can use normal file copying
+	tools to transfer a Mercurial repository onto, for example, a
+	USB thumb drive, and safely move that drive and repository
+	back and forth between a Mac, a PC running Windows, and a
+	Linux box.</para>
+
+    </sect2>
+    <sect2>
+      <title>Detecting case conflicts</title>
+
+      <para>When operating in the working directory, Mercurial honours
+	the naming policy of the filesystem where the working
+	directory is located.  If the filesystem is case preserving,
+	but insensitive, Mercurial will treat names that differ only
+	in case as the same.</para>
+
+      <para>An important aspect of this approach is that it is
+	possible to commit a changeset on a case sensitive (typically
+	Linux or Unix) filesystem that will cause trouble for users on
+	case insensitive (usually Windows and MacOS) users.  If a
+	Linux user commits changes to two files, one named
+	<filename>myfile.c</filename> and the other named
+	<filename>MyFile.C</filename>, they will be stored correctly
+	in the repository.  And in the working directories of other
+	Linux users, they will be correctly represented as separate
+	files.</para>
+
+      <para>If a Windows or Mac user pulls this change, they will not
+	initially have a problem, because Mercurial's repository
+	storage mechanism is case safe.  However, once they try to
+	<command role="hg-cmd">hg update</command> the working
+	directory to that changeset, or <command role="hg-cmd">hg
+	  merge</command> with that changeset, Mercurial will spot the
+	conflict between the two file names that the filesystem would
+	treat as the same, and forbid the update or merge from
+	occurring.</para>
+
+    </sect2>
+    <sect2>
+      <title>Fixing a case conflict</title>
+
+      <para>If you are using Windows or a Mac in a mixed environment
+	where some of your collaborators are using Linux or Unix, and
+	Mercurial reports a case folding conflict when you try to
+	<command role="hg-cmd">hg update</command> or <command
+	  role="hg-cmd">hg merge</command>, the procedure to fix the
+	problem is simple.</para>
+
+      <para>Just find a nearby Linux or Unix box, clone the problem
+	repository onto it, and use Mercurial's <command
+	  role="hg-cmd">hg rename</command> command to change the
+	names of any offending files or directories so that they will
+	no longer cause case folding conflicts.  Commit this change,
+	<command role="hg-cmd">hg pull</command> or <command
+	  role="hg-cmd">hg push</command> it across to your Windows or
+	MacOS system, and <command role="hg-cmd">hg update</command>
+	to the revision with the non-conflicting names.</para>
+
+      <para>The changeset with case-conflicting names will remain in
+	your project's history, and you still won't be able to
+	<command role="hg-cmd">hg update</command> your working
+	directory to that changeset on a Windows or MacOS system, but
+	you can continue development unimpeded.</para>
+
+      <note>
+	<para>  Prior to version 0.9.3, Mercurial did not use a case
+	  safe repository storage mechanism, and did not detect case
+	  folding conflicts.  If you are using an older version of
+	  Mercurial on Windows or MacOS, I strongly recommend that you
+	  upgrade.</para>
+      </note>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch08-branch.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch08-branch.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,485 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:branch">
+  <title>Managing releases and branchy development</title>
+
+  <para>Mercurial provides several mechanisms for you to manage a
+    project that is making progress on multiple fronts at once.  To
+    understand these mechanisms, let's first take a brief look at a
+    fairly normal software project structure.</para>
+
+  <para>Many software projects issue periodic <quote>major</quote>
+    releases that contain substantial new features.  In parallel, they
+    may issue <quote>minor</quote> releases.  These are usually
+    identical to the major releases off which they're based, but with
+    a few bugs fixed.</para>
+
+  <para>In this chapter, we'll start by talking about how to keep
+    records of project milestones such as releases.  We'll then
+    continue on to talk about the flow of work between different
+    phases of a project, and how Mercurial can help you to isolate and
+    manage this work.</para>
+
+  <sect1>
+    <title>Giving a persistent name to a revision</title>
+
+    <para>Once you decide that you'd like to call a particular
+      revision a <quote>release</quote>, it's a good idea to record
+      the identity of that revision. This will let you reproduce that
+      release at a later date, for whatever purpose you might need at
+      the time (reproducing a bug, porting to a new platform, etc).
+      <!-- &interaction.tag.init; --></para>
+
+    <para>Mercurial lets you give a permanent name to any revision
+      using the <command role="hg-cmd">hg tag</command> command.  Not
+      surprisingly, these names are called <quote>tags</quote>. <!--
+      &interaction.tag.tag; --></para>
+
+    <para>A tag is nothing more than a <quote>symbolic name</quote>
+      for a revision.  Tags exist purely for your convenience, so that
+      you have a handy permanent way to refer to a revision; Mercurial
+      doesn't interpret the tag names you use in any way.  Neither
+      does Mercurial place any restrictions on the name of a tag,
+      beyond a few that are necessary to ensure that a tag can be
+      parsed unambiguously.  A tag name cannot contain any of the
+      following characters:</para>
+    <itemizedlist>
+      <listitem><para>Colon (ASCII 58,
+	  <quote><literal>:</literal></quote>)</para>
+      </listitem>
+      <listitem><para>Carriage return (ASCII 13,
+	  <quote><literal>\r</literal></quote>)</para>
+      </listitem>
+      <listitem><para>Newline (ASCII 10,
+	  <quote><literal>\n</literal></quote>)</para>
+      </listitem></itemizedlist>
+
+    <para>You can use the <command role="hg-cmd">hg tags</command>
+      command to display the tags present in your repository.  In the
+      output, each tagged revision is identified first by its name,
+      then by revision number, and finally by the unique hash of the
+      revision. <!-- &interaction.tag.tags; --> Notice that
+      <literal>tip</literal> is listed in the output of <command
+	role="hg-cmd">hg tags</command>.  The <literal>tip</literal>
+      tag is a special <quote>floating</quote> tag, which always
+      identifies the newest revision in the repository.</para>
+
+    <para>In the output of the <command role="hg-cmd">hg
+	tags</command> command, tags are listed in reverse order, by
+      revision number.  This usually means that recent tags are listed
+      before older tags.  It also means that <literal>tip</literal> is
+      always going to be the first tag listed in the output of
+      <command role="hg-cmd">hg tags</command>.</para>
+
+    <para>When you run <command role="hg-cmd">hg log</command>, if it
+      displays a revision that has tags associated with it, it will
+      print those tags. <!-- &interaction.tag.log; --></para>
+
+    <para>Any time you need to provide a revision ID to a Mercurial
+      command, the command will accept a tag name in its place.
+      Internally, Mercurial will translate your tag name into the
+      corresponding revision ID, then use that. <!--
+      &interaction.tag.log.v1.0; --></para>
+
+    <para>There's no limit on the number of tags you can have in a
+      repository, or on the number of tags that a single revision can
+      have.  As a practical matter, it's not a great idea to have
+      <quote>too many</quote> (a number which will vary from project
+      to project), simply because tags are supposed to help you to
+      find revisions.  If you have lots of tags, the ease of using
+      them to identify revisions diminishes rapidly.</para>
+
+    <para>For example, if your project has milestones as frequent as
+      every few days, it's perfectly reasonable to tag each one of
+      those.  But if you have a continuous build system that makes
+      sure every revision can be built cleanly, you'd be introducing a
+      lot of noise if you were to tag every clean build.  Instead, you
+      could tag failed builds (on the assumption that they're rare!),
+      or simply not use tags to track buildability.</para>
+
+    <para>If you want to remove a tag that you no longer want, use
+      <command role="hg-cmd">hg tag --remove</command>. <!--
+      &interaction.tag.remove; --> You can also modify a tag at any
+      time, so that it identifies a different revision, by simply
+      issuing a new <command role="hg-cmd">hg tag</command> command.
+      You'll have to use the <option role="hg-opt-tag">-f</option>
+      option to tell Mercurial that you <emphasis>really</emphasis>
+      want to update the tag. <!-- &interaction.tag.replace; --> There
+      will still be a permanent record of the previous identity of the
+      tag, but Mercurial will no longer use it.  There's thus no
+      penalty to tagging the wrong revision; all you have to do is
+      turn around and tag the correct revision once you discover your
+      error.</para>
+
+    <para>Mercurial stores tags in a normal revision-controlled file
+      in your repository.  If you've created any tags, you'll find
+      them in a file named <filename
+	role="special">.hgtags</filename>.  When you run the <command
+	role="hg-cmd">hg tag</command> command, Mercurial modifies
+      this file, then automatically commits the change to it.  This
+      means that every time you run <command role="hg-cmd">hg
+	tag</command>, you'll see a corresponding changeset in the
+      output of <command role="hg-cmd">hg log</command>. <!--
+      &interaction.tag.tip; --></para>
+
+    <sect2>
+      <title>Handling tag conflicts during a merge</title>
+
+      <para>You won't often need to care about the <filename
+	  role="special">.hgtags</filename> file, but it sometimes
+	makes its presence known during a merge.  The format of the
+	file is simple: it consists of a series of lines.  Each line
+	starts with a changeset hash, followed by a space, followed by
+	the name of a tag.</para>
+
+      <para>If you're resolving a conflict in the <filename
+	  role="special">.hgtags</filename> file during a merge,
+	there's one twist to modifying the <filename
+	  role="special">.hgtags</filename> file: when Mercurial is
+	parsing the tags in a repository, it
+	<emphasis>never</emphasis> reads the working copy of the
+	<filename role="special">.hgtags</filename> file.  Instead, it
+	reads the <emphasis>most recently committed</emphasis>
+	revision of the file.</para>
+
+      <para>An unfortunate consequence of this design is that you
+	can't actually verify that your merged <filename
+	  role="special">.hgtags</filename> file is correct until
+	<emphasis>after</emphasis> you've committed a change.  So if
+	you find yourself resolving a conflict on <filename
+	  role="special">.hgtags</filename> during a merge, be sure to
+	run <command role="hg-cmd">hg tags</command> after you commit.
+	If it finds an error in the <filename
+	  role="special">.hgtags</filename> file, it will report the
+	location of the error, which you can then fix and commit.  You
+	should then run <command role="hg-cmd">hg tags</command>
+	again, just to be sure that your fix is correct.</para>
+
+    </sect2>
+    <sect2>
+      <title>Tags and cloning</title>
+
+      <para>You may have noticed that the <command role="hg-cmd">hg
+	  clone</command> command has a <option
+	  role="hg-opt-clone">-r</option> option that lets you clone
+	an exact copy of the repository as of a particular changeset.
+	The new clone will not contain any project history that comes
+	after the revision you specified.  This has an interaction
+	with tags that can surprise the unwary.</para>
+
+      <para>Recall that a tag is stored as a revision to the <filename
+	  role="special">.hgtags</filename> file, so that when you
+	create a tag, the changeset in which it's recorded necessarily
+	refers to an older changeset.  When you run <command
+	  role="hg-cmd">hg clone -r foo</command> to clone a
+	repository as of tag <literal>foo</literal>, the new clone
+	<emphasis>will not contain the history that created the
+	  tag</emphasis> that you used to clone the repository.  The
+	result is that you'll get exactly the right subset of the
+	project's history in the new repository, but
+	<emphasis>not</emphasis> the tag you might have
+	expected.</para>
+
+    </sect2>
+    <sect2>
+      <title>When permanent tags are too much</title>
+
+      <para>Since Mercurial's tags are revision controlled and carried
+	around with a project's history, everyone you work with will
+	see the tags you create.  But giving names to revisions has
+	uses beyond simply noting that revision
+	<literal>4237e45506ee</literal> is really
+	<literal>v2.0.2</literal>.  If you're trying to track down a
+	subtle bug, you might want a tag to remind you of something
+	like <quote>Anne saw the symptoms with this
+	  revision</quote>.</para>
+
+      <para>For cases like this, what you might want to use are
+	<emphasis>local</emphasis> tags. You can create a local tag
+	with the <option role="hg-opt-tag">-l</option> option to the
+	<command role="hg-cmd">hg tag</command> command.  This will
+	store the tag in a file called <filename
+	  role="special">.hg/localtags</filename>.  Unlike <filename
+	  role="special">.hgtags</filename>, <filename
+	  role="special">.hg/localtags</filename> is not revision
+	controlled.  Any tags you create using <option
+	  role="hg-opt-tag">-l</option> remain strictly local to the
+	repository you're currently working in.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>The flow of changes&emdash;big picture vs. little</title>
+
+    <para>To return to the outline I sketched at the beginning of a
+      chapter, let's think about a project that has multiple
+      concurrent pieces of work under development at once.</para>
+
+    <para>There might be a push for a new <quote>main</quote> release;
+      a new minor bugfix release to the last main release; and an
+      unexpected <quote>hot fix</quote> to an old release that is now
+      in maintenance mode.</para>
+
+    <para>The usual way people refer to these different concurrent
+      directions of development is as <quote>branches</quote>.
+      However, we've already seen numerous times that Mercurial treats
+      <emphasis>all of history</emphasis> as a series of branches and
+      merges.  Really, what we have here is two ideas that are
+      peripherally related, but which happen to share a name.</para>
+    <itemizedlist>
+      <listitem><para><quote>Big picture</quote> branches represent
+	  the sweep of a project's evolution; people give them names,
+	  and talk about them in conversation.</para>
+      </listitem>
+      <listitem><para><quote>Little picture</quote> branches are
+	  artefacts of the day-to-day activity of developing and
+	  merging changes.  They expose the narrative of how the code
+	  was developed.</para>
+      </listitem></itemizedlist>
+
+  </sect1>
+  <sect1>
+    <title>Managing big-picture branches in repositories</title>
+
+    <para>The easiest way to isolate a <quote>big picture</quote>
+      branch in Mercurial is in a dedicated repository.  If you have
+      an existing shared repository&emdash;let's call it
+      <literal>myproject</literal>&emdash;that reaches a
+      <quote>1.0</quote> milestone, you can start to prepare for
+      future maintenance releases on top of version 1.0 by tagging the
+      revision from which you prepared the 1.0 release. <!--
+      &interaction.branch-repo.tag; --> You can then clone a new
+      shared <literal>myproject-1.0.1</literal> repository as of that
+      tag. <!-- &interaction.branch-repo.clone; --></para>
+
+    <para>Afterwards, if someone needs to work on a bug fix that ought
+      to go into an upcoming 1.0.1 minor release, they clone the
+      <literal>myproject-1.0.1</literal> repository, make their
+      changes, and push them back. <!--
+      &interaction.branch-repo.bugfix; --> Meanwhile, development for
+      the next major release can continue, isolated and unabated, in
+      the <literal>myproject</literal> repository. <!--
+      &interaction.branch-repo.new; --></para>
+
+  </sect1>
+  <sect1>
+    <title>Don't repeat yourself: merging across branches</title>
+
+    <para>In many cases, if you have a bug to fix on a maintenance
+      branch, the chances are good that the bug exists on your
+      project's main branch (and possibly other maintenance branches,
+      too).  It's a rare developer who wants to fix the same bug
+      multiple times, so let's look at a few ways that Mercurial can
+      help you to manage these bugfixes without duplicating your
+      work.</para>
+
+    <para>In the simplest instance, all you need to do is pull changes
+      from your maintenance branch into your local clone of the target
+      branch. <!-- &interaction.branch-repo.pull; --> You'll then need
+      to merge the heads of the two branches, and push back to the
+      main branch. <!-- &interaction.branch-repo.merge; --></para>
+
+  </sect1>
+  <sect1>
+    <title>Naming branches within one repository</title>
+
+    <para>In most instances, isolating branches in repositories is the
+      right approach.  Its simplicity makes it easy to understand; and
+      so it's hard to make mistakes.  There's a one-to-one
+      relationship between branches you're working in and directories
+      on your system.  This lets you use normal (non-Mercurial-aware)
+      tools to work on files within a branch/repository.</para>
+
+    <para>If you're more in the <quote>power user</quote> category
+      (<emphasis>and</emphasis> your collaborators are too), there is
+      an alternative way of handling branches that you can consider.
+      I've already mentioned the human-level distinction between
+      <quote>small picture</quote> and <quote>big picture</quote>
+      branches.  While Mercurial works with multiple <quote>small
+	picture</quote> branches in a repository all the time (for
+      example after you pull changes in, but before you merge them),
+      it can <emphasis>also</emphasis> work with multiple <quote>big
+	picture</quote> branches.</para>
+
+    <para>The key to working this way is that Mercurial lets you
+      assign a persistent <emphasis>name</emphasis> to a branch.
+      There always exists a branch named <literal>default</literal>.
+      Even before you start naming branches yourself, you can find
+      traces of the <literal>default</literal> branch if you look for
+      them.</para>
+
+    <para>As an example, when you run the <command role="hg-cmd">hg
+	commit</command> command, and it pops up your editor so that
+      you can enter a commit message, look for a line that contains
+      the text <quote><literal>HG: branch default</literal></quote> at
+      the bottom. This is telling you that your commit will occur on
+      the branch named <literal>default</literal>.</para>
+
+    <para>To start working with named branches, use the <command
+	role="hg-cmd">hg branches</command> command.  This command
+      lists the named branches already present in your repository,
+      telling you which changeset is the tip of each. <!--
+      &interaction.branch-named.branches; --> Since you haven't
+      created any named branches yet, the only one that exists is
+      <literal>default</literal>.</para>
+
+    <para>To find out what the <quote>current</quote> branch is, run
+      the <command role="hg-cmd">hg branch</command> command, giving
+      it no arguments.  This tells you what branch the parent of the
+      current changeset is on. <!-- &interaction.branch-named.branch;
+      --></para>
+
+    <para>To create a new branch, run the <command role="hg-cmd">hg
+	branch</command> command again.  This time, give it one
+      argument: the name of the branch you want to create. <!--
+      &interaction.branch-named.create; --></para>
+
+    <para>After you've created a branch, you might wonder what effect
+      the <command role="hg-cmd">hg branch</command> command has had.
+      What do the <command role="hg-cmd">hg status</command> and
+      <command role="hg-cmd">hg tip</command> commands report? <!--
+      &interaction.branch-named.status; --> Nothing has changed in the
+      working directory, and there's been no new history created.  As
+      this suggests, running the <command role="hg-cmd">hg
+	branch</command> command has no permanent effect; it only
+      tells Mercurial what branch name to use the
+      <emphasis>next</emphasis> time you commit a changeset.</para>
+
+    <para>When you commit a change, Mercurial records the name of the
+      branch on which you committed.  Once you've switched from the
+      <literal>default</literal> branch to another and committed,
+      you'll see the name of the new branch show up in the output of
+      <command role="hg-cmd">hg log</command>, <command
+	role="hg-cmd">hg tip</command>, and other commands that
+      display the same kind of output. <!--
+      &interaction.branch-named.commit; --> The <command
+	role="hg-cmd">hg log</command>-like commands will print the
+      branch name of every changeset that's not on the
+      <literal>default</literal> branch.  As a result, if you never
+      use named branches, you'll never see this information.</para>
+
+    <para>Once you've named a branch and committed a change with that
+      name, every subsequent commit that descends from that change
+      will inherit the same branch name.  You can change the name of a
+      branch at any time, using the <command role="hg-cmd">hg
+	branch</command> command. <!--
+      &interaction.branch-named.rebranch; --> In practice, this is
+      something you won't do very often, as branch names tend to have
+      fairly long lifetimes.  (This isn't a rule, just an
+      observation.)</para>
+
+  </sect1>
+  <sect1>
+    <title>Dealing with multiple named branches in a
+      repository</title>
+
+    <para>If you have more than one named branch in a repository,
+      Mercurial will remember the branch that your working directory
+      on when you start a command like <command role="hg-cmd">hg
+	update</command> or <command role="hg-cmd">hg pull
+	-u</command>.  It will update the working directory to the tip
+      of this branch, no matter what the <quote>repo-wide</quote> tip
+      is.  To update to a revision that's on a different named branch,
+      you may need to use the <option role="hg-opt-update">-C</option>
+      option to <command role="hg-cmd">hg update</command>.</para>
+
+    <para>This behaviour is a little subtle, so let's see it in
+      action.  First, let's remind ourselves what branch we're
+      currently on, and what branches are in our repository. <!--
+      &interaction.branch-named.parents; --> We're on the
+      <literal>bar</literal> branch, but there also exists an older
+      <command role="hg-cmd">hg foo</command> branch.</para>
+
+    <para>We can <command role="hg-cmd">hg update</command> back and
+      forth between the tips of the <literal>foo</literal> and
+      <literal>bar</literal> branches without needing to use the
+      <option role="hg-opt-update">-C</option> option, because this
+      only involves going backwards and forwards linearly through our
+      change history. <!-- &interaction.branch-named.update-switchy;
+      --></para>
+
+    <para>If we go back to the <literal>foo</literal> branch and then
+      run <command role="hg-cmd">hg update</command>, it will keep us
+      on <literal>foo</literal>, not move us to the tip of
+      <literal>bar</literal>. <!--
+      &interaction.branch-named.update-nothing; --></para>
+
+    <para>Committing a new change on the <literal>foo</literal> branch
+      introduces a new head. <!--
+      &interaction.branch-named.foo-commit; --></para>
+
+  </sect1>
+  <sect1>
+    <title>Branch names and merging</title>
+
+    <para>As you've probably noticed, merges in Mercurial are not
+      symmetrical. Let's say our repository has two heads, 17 and 23.
+      If I <command role="hg-cmd">hg update</command> to 17 and then
+      <command role="hg-cmd">hg merge</command> with 23, Mercurial
+      records 17 as the first parent of the merge, and 23 as the
+      second.  Whereas if I <command role="hg-cmd">hg update</command>
+      to 23 and then <command role="hg-cmd">hg merge</command> with
+      17, it records 23 as the first parent, and 17 as the
+      second.</para>
+
+    <para>This affects Mercurial's choice of branch name when you
+      merge.  After a merge, Mercurial will retain the branch name of
+      the first parent when you commit the result of the merge.  If
+      your first parent's branch name is <literal>foo</literal>, and
+      you merge with <literal>bar</literal>, the branch name will
+      still be <literal>foo</literal> after you merge.</para>
+
+    <para>It's not unusual for a repository to contain multiple heads,
+      each with the same branch name.  Let's say I'm working on the
+      <literal>foo</literal> branch, and so are you.  We commit
+      different changes; I pull your changes; I now have two heads,
+      each claiming to be on the <literal>foo</literal> branch.  The
+      result of a merge will be a single head on the
+      <literal>foo</literal> branch, as you might hope.</para>
+
+    <para>But if I'm working on the <literal>bar</literal> branch, and
+      I merge work from the <literal>foo</literal> branch, the result
+      will remain on the <literal>bar</literal> branch. <!--
+      &interaction.branch-named.merge; --></para>
+
+    <para>To give a more concrete example, if I'm working on the
+      <literal>bleeding-edge</literal> branch, and I want to bring in
+      the latest fixes from the <literal>stable</literal> branch,
+      Mercurial will choose the <quote>right</quote>
+      (<literal>bleeding-edge</literal>) branch name when I pull and
+      merge from <literal>stable</literal>.</para>
+
+  </sect1>
+  <sect1>
+    <title>Branch naming is generally useful</title>
+
+    <para>You shouldn't think of named branches as applicable only to
+      situations where you have multiple long-lived branches
+      cohabiting in a single repository.  They're very useful even in
+      the one-branch-per-repository case.</para>
+
+    <para>In the simplest case, giving a name to each branch gives you
+      a permanent record of which branch a changeset originated on.
+      This gives you more context when you're trying to follow the
+      history of a long-lived branchy project.</para>
+
+    <para>If you're working with shared repositories, you can set up a
+      <literal role="hook">pretxnchangegroup</literal> hook on each
+      that will block incoming changes that have the
+      <quote>wrong</quote> branch name.  This provides a simple, but
+      effective, defence against people accidentally pushing changes
+      from a <quote>bleeding edge</quote> branch to a
+      <quote>stable</quote> branch.  Such a hook might look like this
+      inside the shared repo's <filename role="special">
+	/.hgrc</filename>.</para>
+    <programlisting>[hooks] pretxnchangegroup.branch = hg heads
+      --template '{branches} ' | grep mybranch</programlisting>
+
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch09-undo.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch09-undo.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,997 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:undo">
+  <title>Finding and fixing your mistakes</title>
+
+  <para>To err might be human, but to really handle the consequences
+    well takes a top-notch revision control system.  In this chapter,
+    we'll discuss some of the techniques you can use when you find
+    that a problem has crept into your project.  Mercurial has some
+    highly capable features that will help you to isolate the sources
+    of problems, and to handle them appropriately.</para>
+
+  <sect1>
+    <title>Erasing local history</title>
+
+    <sect2>
+      <title>The accidental commit</title>
+
+      <para>I have the occasional but persistent problem of typing
+	rather more quickly than I can think, which sometimes results
+	in me committing a changeset that is either incomplete or
+	plain wrong.  In my case, the usual kind of incomplete
+	changeset is one in which I've created a new source file, but
+	forgotten to <command role="hg-cmd">hg add</command> it.  A
+	<quote>plain wrong</quote> changeset is not as common, but no
+	less annoying.</para>
+
+    </sect2>
+    <sect2 id="sec:undo:rollback">
+      <title>Rolling back a transaction</title>
+
+      <para>In section <xref linkend="sec:concepts:txn"/>, I mentioned
+	that Mercurial treats each modification of a repository as a
+	<emphasis>transaction</emphasis>.  Every time you commit a
+	changeset or pull changes from another repository, Mercurial
+	remembers what you did.  You can undo, or <emphasis>roll
+	  back</emphasis>, exactly one of these actions using the
+	<command role="hg-cmd">hg rollback</command> command.  (See
+	section <xref linkend="sec:undo:rollback-after-push"/> for an
+	important caveat about the use of this command.)</para>
+
+      <para>Here's a mistake that I often find myself making:
+	committing a change in which I've created a new file, but
+	forgotten to <command role="hg-cmd">hg add</command> it. <!--
+	&interaction.rollback.commit; --> Looking at the output of
+	<command role="hg-cmd">hg status</command> after the commit
+	immediately confirms the error. <!--
+	&interaction.rollback.status; --> The commit captured the
+	changes to the file <filename>a</filename>, but not the new
+	file <filename>b</filename>.  If I were to push this changeset
+	to a repository that I shared with a colleague, the chances
+	are high that something in <filename>a</filename> would refer
+	to <filename>b</filename>, which would not be present in their
+	repository when they pulled my changes.  I would thus become
+	the object of some indignation.</para>
+
+      <para>However, luck is with me&emdash;I've caught my error
+	before I pushed the changeset.  I use the <command
+	  role="hg-cmd">hg rollback</command> command, and Mercurial
+	makes that last changeset vanish. <!--
+	&interaction.rollback.rollback; --> Notice that the changeset
+	is no longer present in the repository's history, and the
+	working directory once again thinks that the file
+	<filename>a</filename> is modified.  The commit and rollback
+	have left the working directory exactly as it was prior to the
+	commit; the changeset has been completely erased.  I can now
+	safely <command role="hg-cmd">hg add</command> the file
+	<filename>b</filename>, and rerun my commit. <!--
+	&interaction.rollback.add; --></para>
+
+    </sect2>
+    <sect2>
+      <title>The erroneous pull</title>
+
+      <para>It's common practice with Mercurial to maintain separate
+	development branches of a project in different repositories.
+	Your development team might have one shared repository for
+	your project's <quote>0.9</quote> release, and another,
+	containing different changes, for the <quote>1.0</quote>
+	release.</para>
+
+      <para>Given this, you can imagine that the consequences could be
+	messy if you had a local <quote>0.9</quote> repository, and
+	accidentally pulled changes from the shared <quote>1.0</quote>
+	repository into it.  At worst, you could be paying
+	insufficient attention, and push those changes into the shared
+	<quote>0.9</quote> tree, confusing your entire team (but don't
+	worry, we'll return to this horror scenario later).  However,
+	it's more likely that you'll notice immediately, because
+	Mercurial will display the URL it's pulling from, or you will
+	see it pull a suspiciously large number of changes into the
+	repository.</para>
+
+      <para>The <command role="hg-cmd">hg rollback</command> command
+	will work nicely to expunge all of the changesets that you
+	just pulled.  Mercurial groups all changes from one <command
+	  role="hg-cmd">hg pull</command> into a single transaction,
+	so one <command role="hg-cmd">hg rollback</command> is all you
+	need to undo this mistake.</para>
+
+    </sect2>
+    <sect2 id="sec:undo:rollback-after-push">
+      <title>Rolling back is useless once you've pushed</title>
+
+      <para>The value of the <command role="hg-cmd">hg
+	  rollback</command> command drops to zero once you've pushed
+	your changes to another repository.  Rolling back a change
+	makes it disappear entirely, but <emphasis>only</emphasis> in
+	the repository in which you perform the <command
+	  role="hg-cmd">hg rollback</command>.  Because a rollback
+	eliminates history, there's no way for the disappearance of a
+	change to propagate between repositories.</para>
+
+      <para>If you've pushed a change to another
+	repository&emdash;particularly if it's a shared
+	repository&emdash;it has essentially <quote>escaped into the
+	  wild,</quote> and you'll have to recover from your mistake
+	in a different way.  What will happen if you push a changeset
+	somewhere, then roll it back, then pull from the repository
+	you pushed to, is that the changeset will reappear in your
+	repository.</para>
+
+      <para>(If you absolutely know for sure that the change you want
+	to roll back is the most recent change in the repository that
+	you pushed to, <emphasis>and</emphasis> you know that nobody
+	else could have pulled it from that repository, you can roll
+	back the changeset there, too, but you really should really
+	not rely on this working reliably.  If you do this, sooner or
+	later a change really will make it into a repository that you
+	don't directly control (or have forgotten about), and come
+	back to bite you.)</para>
+
+    </sect2>
+    <sect2>
+      <title>You can only roll back once</title>
+
+      <para>Mercurial stores exactly one transaction in its
+	transaction log; that transaction is the most recent one that
+	occurred in the repository. This means that you can only roll
+	back one transaction.  If you expect to be able to roll back
+	one transaction, then its predecessor, this is not the
+	behaviour you will get. <!-- &interaction.rollback.twice; -->
+	Once you've rolled back one transaction in a repository, you
+	can't roll back again in that repository until you perform
+	another commit or pull.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Reverting the mistaken change</title>
+
+    <para>If you make a modification to a file, and decide that you
+      really didn't want to change the file at all, and you haven't
+      yet committed your changes, the <command role="hg-cmd">hg
+	revert</command> command is the one you'll need.  It looks at
+      the changeset that's the parent of the working directory, and
+      restores the contents of the file to their state as of that
+      changeset. (That's a long-winded way of saying that, in the
+      normal case, it undoes your modifications.)</para>
+
+    <para>Let's illustrate how the <command role="hg-cmd">hg
+	revert</command> command works with yet another small example.
+      We'll begin by modifying a file that Mercurial is already
+      tracking. <!-- &interaction.daily.revert.modify; --> If we don't
+      want that change, we can simply <command role="hg-cmd">hg
+	revert</command> the file. <!--
+      &interaction.daily.revert.unmodify; --> The <command
+	role="hg-cmd">hg revert</command> command provides us with an
+      extra degree of safety by saving our modified file with a
+      <filename>.orig</filename> extension. <!--
+      &interaction.daily.revert.status; --></para>
+
+    <para>Here is a summary of the cases that the <command
+	role="hg-cmd">hg revert</command> command can deal with.  We
+      will describe each of these in more detail in the section that
+      follows.</para>
+    <itemizedlist>
+      <listitem><para>If you modify a file, it will restore the file
+	  to its unmodified state.</para>
+      </listitem>
+      <listitem><para>If you <command role="hg-cmd">hg add</command> a
+	  file, it will undo the <quote>added</quote> state of the
+	  file, but leave the file itself untouched.</para>
+      </listitem>
+      <listitem><para>If you delete a file without telling Mercurial,
+	  it will restore the file to its unmodified contents.</para>
+      </listitem>
+      <listitem><para>If you use the <command role="hg-cmd">hg
+	    remove</command> command to remove a file, it will undo
+	  the <quote>removed</quote> state of the file, and restore
+	  the file to its unmodified contents.</para>
+      </listitem></itemizedlist>
+
+    <sect2 id="sec:undo:mgmt">
+      <title>File management errors</title>
+
+      <para>The <command role="hg-cmd">hg revert</command> command is
+	useful for more than just modified files.  It lets you reverse
+	the results of all of Mercurial's file management
+	commands&emdash;<command role="hg-cmd">hg add</command>,
+	<command role="hg-cmd">hg remove</command>, and so on.</para>
+
+      <para>If you <command role="hg-cmd">hg add</command> a file,
+	then decide that in fact you don't want Mercurial to track it,
+	use <command role="hg-cmd">hg revert</command> to undo the
+	add.  Don't worry; Mercurial will not modify the file in any
+	way.  It will just <quote>unmark</quote> the file. <!--
+	&interaction.daily.revert.add; --></para>
+
+      <para>Similarly, if you ask Mercurial to <command
+	  role="hg-cmd">hg remove</command> a file, you can use
+	<command role="hg-cmd">hg revert</command> to restore it to
+	the contents it had as of the parent of the working directory.
+	<!-- &interaction.daily.revert.remove; --> This works just as
+	well for a file that you deleted by hand, without telling
+	Mercurial (recall that in Mercurial terminology, this kind of
+	file is called <quote>missing</quote>). <!--
+	&interaction.daily.revert.missing; --></para>
+
+      <para>If you revert a <command role="hg-cmd">hg copy</command>,
+	the copied-to file remains in your working directory
+	afterwards, untracked.  Since a copy doesn't affect the
+	copied-from file in any way, Mercurial doesn't do anything
+	with the copied-from file. <!--
+	&interaction.daily.revert.copy; --></para>
+
+      <sect3>
+	<title>A slightly special case: reverting a rename</title>
+
+	<para>If you <command role="hg-cmd">hg rename</command> a
+	  file, there is one small detail that you should remember.
+	  When you <command role="hg-cmd">hg revert</command> a
+	  rename, it's not enough to provide the name of the
+	  renamed-to file, as you can see here. <!--
+	  &interaction.daily.revert.rename; --> As you can see from
+	  the output of <command role="hg-cmd">hg status</command>,
+	  the renamed-to file is no longer identified as added, but
+	  the renamed-<emphasis>from</emphasis> file is still removed!
+	  This is counter-intuitive (at least to me), but at least
+	  it's easy to deal with. <!--
+	  &interaction.daily.revert.rename-orig; --> So remember, to
+	  revert a <command role="hg-cmd">hg rename</command>, you
+	  must provide <emphasis>both</emphasis> the source and
+	  destination names.</para>
+
+	<para>% TODO: the output doesn't look like it will be
+	  removed!</para>
+
+	<para>(By the way, if you rename a file, then modify the
+	  renamed-to file, then revert both components of the rename,
+	  when Mercurial restores the file that was removed as part of
+	  the rename, it will be unmodified. If you need the
+	  modifications in the renamed-to file to show up in the
+	  renamed-from file, don't forget to copy them over.)</para>
+
+	<para>These fiddly aspects of reverting a rename arguably
+	  constitute a small bug in Mercurial.</para>
+
+      </sect3>
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Dealing with committed changes</title>
+
+    <para>Consider a case where you have committed a change $a$, and
+      another change $b$ on top of it; you then realise that change
+      $a$ was incorrect.  Mercurial lets you <quote>back out</quote>
+      an entire changeset automatically, and building blocks that let
+      you reverse part of a changeset by hand.</para>
+
+    <para>Before you read this section, here's something to keep in
+      mind: the <command role="hg-cmd">hg backout</command> command
+      undoes changes by <emphasis>adding</emphasis> history, not by
+      modifying or erasing it.  It's the right tool to use if you're
+      fixing bugs, but not if you're trying to undo some change that
+      has catastrophic consequences.  To deal with those, see section
+      <xref linkend="sec:undo:aaaiiieee"/>.</para>
+
+    <sect2>
+      <title>Backing out a changeset</title>
+
+      <para>The <command role="hg-cmd">hg backout</command> command
+	lets you <quote>undo</quote> the effects of an entire
+	changeset in an automated fashion.  Because Mercurial's
+	history is immutable, this command <emphasis>does
+	  not</emphasis> get rid of the changeset you want to undo.
+	Instead, it creates a new changeset that
+	<emphasis>reverses</emphasis> the effect of the to-be-undone
+	changeset.</para>
+
+      <para>The operation of the <command role="hg-cmd">hg
+	  backout</command> command is a little intricate, so let's
+	illustrate it with some examples.  First, we'll create a
+	repository with some simple changes. <!--
+	&interaction.backout.init; --></para>
+
+      <para>The <command role="hg-cmd">hg backout</command> command
+	takes a single changeset ID as its argument; this is the
+	changeset to back out.  Normally, <command role="hg-cmd">hg
+	  backout</command> will drop you into a text editor to write
+	a commit message, so you can record why you're backing the
+	change out.  In this example, we provide a commit message on
+	the command line using the <option
+	  role="hg-opt-backout">-m</option> option.</para>
+
+    </sect2>
+    <sect2>
+      <title>Backing out the tip changeset</title>
+
+      <para>We're going to start by backing out the last changeset we
+	committed. <!-- &interaction.backout.simple; --> You can see
+	that the second line from <filename>myfile</filename> is no
+	longer present.  Taking a look at the output of <command
+	  role="hg-cmd">hg log</command> gives us an idea of what the
+	<command role="hg-cmd">hg backout</command> command has done.
+	<!-- &interaction.backout.simple.log; --> Notice that the new
+	changeset that <command role="hg-cmd">hg backout</command> has
+	created is a child of the changeset we backed out.  It's
+	easier to see this in figure <xref
+	  linkend="fig:undo:backout"/>, which presents a graphical
+	view of the change history.  As you can see, the history is
+	nice and linear.</para>
+
+      <informalfigure id="fig:undo:backout">
+	<mediaobject><imageobject><imagedata
+				    fileref="undo-simple"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Backing out
+	      a change using the <command role="hg-cmd">hg
+		backout</command>
+	      command</para></caption></mediaobject>
+	
+      </informalfigure>
+
+    </sect2>
+    <sect2>
+      <title>Backing out a non-tip change</title>
+
+      <para>If you want to back out a change other than the last one
+	you committed, pass the <option
+	  role="hg-opt-backout">--merge</option> option to the
+	<command role="hg-cmd">hg backout</command> command. <!--
+	&interaction.backout.non-tip.clone; --> This makes backing out
+	any changeset a <quote>one-shot</quote> operation that's
+	usually simple and fast. <!--
+	&interaction.backout.non-tip.backout; --></para>
+
+      <para>If you take a look at the contents of
+	<filename>myfile</filename> after the backout finishes, you'll
+	see that the first and third changes are present, but not the
+	second. <!-- &interaction.backout.non-tip.cat; --></para>
+
+      <para>As the graphical history in figure <xref
+	  linkend="fig:undo:backout-non-tip"/> illustrates, Mercurial
+	actually commits <emphasis>two</emphasis> changes in this kind
+	of situation (the box-shaped nodes are the ones that Mercurial
+	commits automatically).  Before Mercurial begins the backout
+	process, it first remembers what the current parent of the
+	working directory is.  It then backs out the target changeset,
+	and commits that as a changeset.  Finally, it merges back to
+	the previous parent of the working directory, and commits the
+	result of the merge.</para>
+
+      <para>% TODO: to me it looks like mercurial doesn't commit the
+	second merge automatically!</para>
+
+      <informalfigure id="fig:undo:backout-non-tip">
+	<mediaobject><imageobject><imagedata
+				    fileref="undo-non-tip"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Automated
+	      backout of a non-tip change using the <command
+		role="hg-cmd">hg backout</command>
+	      command</para></caption></mediaobject>
+      </informalfigure>
+
+      <para>The result is that you end up <quote>back where you
+	  were</quote>, only with some extra history that undoes the
+	effect of the changeset you wanted to back out.</para>
+
+      <sect3>
+	<title>Always use the <option
+	    role="hg-opt-backout">--merge</option> option</title>
+
+	<para>In fact, since the <option
+	    role="hg-opt-backout">--merge</option> option will do the
+	  <quote>right thing</quote> whether or not the changeset
+	  you're backing out is the tip (i.e. it won't try to merge if
+	  it's backing out the tip, since there's no need), you should
+	  <emphasis>always</emphasis> use this option when you run the
+	  <command role="hg-cmd">hg backout</command> command.</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Gaining more control of the backout process</title>
+
+      <para>While I've recommended that you always use the <option
+	  role="hg-opt-backout">--merge</option> option when backing
+	out a change, the <command role="hg-cmd">hg backout</command>
+	command lets you decide how to merge a backout changeset.
+	Taking control of the backout process by hand is something you
+	will rarely need to do, but it can be useful to understand
+	what the <command role="hg-cmd">hg backout</command> command
+	is doing for you automatically.  To illustrate this, let's
+	clone our first repository, but omit the backout change that
+	it contains.</para>
+
+      <para><!-- &interaction.backout.manual.clone; --> As with our
+	earlier example, We'll commit a third changeset, then back out
+	its parent, and see what happens. <!--
+	&interaction.backout.manual.backout; --> Our new changeset is
+	again a descendant of the changeset we backout out; it's thus
+	a new head, <emphasis>not</emphasis> a descendant of the
+	changeset that was the tip.  The <command role="hg-cmd">hg
+	  backout</command> command was quite explicit in telling us
+	this. <!-- &interaction.backout.manual.log; --></para>
+
+      <para>Again, it's easier to see what has happened by looking at
+	a graph of the revision history, in figure <xref
+	  linkend="fig:undo:backout-manual"/>.  This makes it clear
+	that when we use <command role="hg-cmd">hg backout</command>
+	to back out a change other than the tip, Mercurial adds a new
+	head to the repository (the change it committed is
+	box-shaped).</para>
+
+      <informalfigure id="fig:undo:backout-manual">
+	<mediaobject><imageobject><imagedata
+				    fileref="undo-manual"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Backing out
+	      a change using the <command role="hg-cmd">hg
+		backout</command>
+	      command</para></caption></mediaobject>
+	
+      </informalfigure>
+
+      <para>After the <command role="hg-cmd">hg backout</command>
+	command has completed, it leaves the new
+	<quote>backout</quote> changeset as the parent of the working
+	directory. <!-- &interaction.backout.manual.parents; --> Now
+	we have two isolated sets of changes. <!--
+	&interaction.backout.manual.heads; --></para>
+
+      <para>Let's think about what we expect to see as the contents of
+	<filename>myfile</filename> now.  The first change should be
+	present, because we've never backed it out.  The second change
+	should be missing, as that's the change we backed out.  Since
+	the history graph shows the third change as a separate head,
+	we <emphasis>don't</emphasis> expect to see the third change
+	present in <filename>myfile</filename>. <!--
+	&interaction.backout.manual.cat; --> To get the third change
+	back into the file, we just do a normal merge of our two
+	heads. <!-- &interaction.backout.manual.merge; --> Afterwards,
+	the graphical history of our repository looks like figure
+	<xref linkend="fig:undo:backout-manual-merge"/>.</para>
+
+      <informalfigure id="fig:undo:backout-manual-merge">
+	<mediaobject><imageobject><imagedata
+				    fileref="undo-manual-merge"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Manually
+	      merging a backout change</para></caption></mediaobject>
+	
+      </informalfigure>
+
+    </sect2>
+    <sect2>
+      <title>Why <command role="hg-cmd">hg backout</command> works as
+	it does</title>
+
+      <para>Here's a brief description of how the <command
+	  role="hg-cmd">hg backout</command> command works.</para>
+      <orderedlist>
+	<listitem><para>It ensures that the working directory is
+	    <quote>clean</quote>, i.e. that the output of <command
+	      role="hg-cmd">hg status</command> would be empty.</para>
+	</listitem>
+	<listitem><para>It remembers the current parent of the working
+	    directory.  Let's call this changeset
+	    <literal>orig</literal></para>
+	</listitem>
+	<listitem><para>It does the equivalent of a <command
+	      role="hg-cmd">hg update</command> to sync the working
+	    directory to the changeset you want to back out.  Let's
+	    call this changeset <literal>backout</literal></para>
+	</listitem>
+	<listitem><para>It finds the parent of that changeset.  Let's
+	    call that changeset <literal>parent</literal>.</para>
+	</listitem>
+	<listitem><para>For each file that the
+	    <literal>backout</literal> changeset affected, it does the
+	    equivalent of a <command role="hg-cmd">hg revert -r
+	      parent</command> on that file, to restore it to the
+	    contents it had before that changeset was
+	    committed.</para>
+	</listitem>
+	<listitem><para>It commits the result as a new changeset.
+	    This changeset has <literal>backout</literal> as its
+	    parent.</para>
+	</listitem>
+	<listitem><para>If you specify <option
+	      role="hg-opt-backout">--merge</option> on the command
+	    line, it merges with <literal>orig</literal>, and commits
+	    the result of the merge.</para>
+	</listitem></orderedlist>
+
+      <para>An alternative way to implement the <command
+	  role="hg-cmd">hg backout</command> command would be to
+	<command role="hg-cmd">hg export</command> the
+	to-be-backed-out changeset as a diff, then use the <option
+	  role="cmd-opt-patch">--reverse</option> option to the
+	<command>patch</command> command to reverse the effect of the
+	change without fiddling with the working directory.  This
+	sounds much simpler, but it would not work nearly as
+	well.</para>
+
+      <para>The reason that <command role="hg-cmd">hg
+	  backout</command> does an update, a commit, a merge, and
+	another commit is to give the merge machinery the best chance
+	to do a good job when dealing with all the changes
+	<emphasis>between</emphasis> the change you're backing out and
+	the current tip.</para>
+
+      <para>If you're backing out a changeset that's 100 revisions
+	back in your project's history, the chances that the
+	<command>patch</command> command will be able to apply a
+	reverse diff cleanly are not good, because intervening changes
+	are likely to have <quote>broken the context</quote> that
+	<command>patch</command> uses to determine whether it can
+	apply a patch (if this sounds like gibberish, see <xref
+	  linkend="sec:mq:patch"/> for a
+	discussion of the <command>patch</command> command).  Also,
+	Mercurial's merge machinery will handle files and directories
+	being renamed, permission changes, and modifications to binary
+	files, none of which <command>patch</command> can deal
+	with.</para>
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:undo:aaaiiieee">
+    <title>Changes that should never have been</title>
+
+    <para>Most of the time, the <command role="hg-cmd">hg
+	backout</command> command is exactly what you need if you want
+      to undo the effects of a change.  It leaves a permanent record
+      of exactly what you did, both when committing the original
+      changeset and when you cleaned up after it.</para>
+
+    <para>On rare occasions, though, you may find that you've
+      committed a change that really should not be present in the
+      repository at all.  For example, it would be very unusual, and
+      usually considered a mistake, to commit a software project's
+      object files as well as its source files.  Object files have
+      almost no intrinsic value, and they're <emphasis>big</emphasis>,
+      so they increase the size of the repository and the amount of
+      time it takes to clone or pull changes.</para>
+
+    <para>Before I discuss the options that you have if you commit a
+      <quote>brown paper bag</quote> change (the kind that's so bad
+      that you want to pull a brown paper bag over your head), let me
+      first discuss some approaches that probably won't work.</para>
+
+    <para>Since Mercurial treats history as accumulative&emdash;every
+      change builds on top of all changes that preceded it&emdash;you
+      generally can't just make disastrous changes disappear.  The one
+      exception is when you've just committed a change, and it hasn't
+      been pushed or pulled into another repository.  That's when you
+      can safely use the <command role="hg-cmd">hg rollback</command>
+      command, as I detailed in section <xref
+	linkend="sec:undo:rollback"/>.</para>
+
+    <para>After you've pushed a bad change to another repository, you
+      <emphasis>could</emphasis> still use <command role="hg-cmd">hg
+	rollback</command> to make your local copy of the change
+      disappear, but it won't have the consequences you want.  The
+      change will still be present in the remote repository, so it
+      will reappear in your local repository the next time you
+      pull.</para>
+
+    <para>If a situation like this arises, and you know which
+      repositories your bad change has propagated into, you can
+      <emphasis>try</emphasis> to get rid of the changeefrom
+      <emphasis>every</emphasis> one of those repositories.  This is,
+      of course, not a satisfactory solution: if you miss even a
+      single repository while you're expunging, the change is still
+      <quote>in the wild</quote>, and could propagate further.</para>
+
+    <para>If you've committed one or more changes
+      <emphasis>after</emphasis> the change that you'd like to see
+      disappear, your options are further reduced. Mercurial doesn't
+      provide a way to <quote>punch a hole</quote> in history, leaving
+      changesets intact.</para>
+
+    <para>XXX This needs filling out.  The
+      <literal>hg-replay</literal> script in the
+      <literal>examples</literal> directory works, but doesn't handle
+      merge changesets.  Kind of an important omission.</para>
+
+    <sect2>
+      <title>Protect yourself from <quote>escaped</quote>
+	changes</title>
+
+      <para>If you've committed some changes to your local repository
+	and they've been pushed or pulled somewhere else, this isn't
+	necessarily a disaster.  You can protect yourself ahead of
+	time against some classes of bad changeset.  This is
+	particularly easy if your team usually pulls changes from a
+	central repository.</para>
+
+      <para>By configuring some hooks on that repository to validate
+	incoming changesets (see chapter <xref linkend="chap:hook"/>),
+	you can
+	automatically prevent some kinds of bad changeset from being
+	pushed to the central repository at all.  With such a
+	configuration in place, some kinds of bad changeset will
+	naturally tend to <quote>die out</quote> because they can't
+	propagate into the central repository.  Better yet, this
+	happens without any need for explicit intervention.</para>
+
+      <para>For instance, an incoming change hook that verifies that a
+	changeset will actually compile can prevent people from
+	inadvertantly <quote>breaking the build</quote>.</para>
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:undo:bisect">
+    <title>Finding the source of a bug</title>
+
+    <para>While it's all very well to be able to back out a changeset
+      that introduced a bug, this requires that you know which
+      changeset to back out.  Mercurial provides an invaluable
+      command, called <command role="hg-cmd">hg bisect</command>, that
+      helps you to automate this process and accomplish it very
+      efficiently.</para>
+
+    <para>The idea behind the <command role="hg-cmd">hg
+	bisect</command> command is that a changeset has introduced
+      some change of behaviour that you can identify with a simple
+      binary test.  You don't know which piece of code introduced the
+      change, but you know how to test for the presence of the bug.
+      The <command role="hg-cmd">hg bisect</command> command uses your
+      test to direct its search for the changeset that introduced the
+      code that caused the bug.</para>
+
+    <para>Here are a few scenarios to help you understand how you
+      might apply this command.</para>
+    <itemizedlist>
+      <listitem><para>The most recent version of your software has a
+	  bug that you remember wasn't present a few weeks ago, but
+	  you don't know when it was introduced.  Here, your binary
+	  test checks for the presence of that bug.</para>
+      </listitem>
+      <listitem><para>You fixed a bug in a rush, and now it's time to
+	  close the entry in your team's bug database.  The bug
+	  database requires a changeset ID when you close an entry,
+	  but you don't remember which changeset you fixed the bug in.
+	  Once again, your binary test checks for the presence of the
+	  bug.</para>
+      </listitem>
+      <listitem><para>Your software works correctly, but runs 15%
+	  slower than the last time you measured it.  You want to know
+	  which changeset introduced the performance regression.  In
+	  this case, your binary test measures the performance of your
+	  software, to see whether it's <quote>fast</quote> or
+	  <quote>slow</quote>.</para>
+      </listitem>
+      <listitem><para>The sizes of the components of your project that
+	  you ship exploded recently, and you suspect that something
+	  changed in the way you build your project.</para>
+      </listitem></itemizedlist>
+
+    <para>From these examples, it should be clear that the <command
+	role="hg-cmd">hg bisect</command> command is not useful only
+      for finding the sources of bugs.  You can use it to find any
+      <quote>emergent property</quote> of a repository (anything that
+      you can't find from a simple text search of the files in the
+      tree) for which you can write a binary test.</para>
+
+    <para>We'll introduce a little bit of terminology here, just to
+      make it clear which parts of the search process are your
+      responsibility, and which are Mercurial's.  A
+      <emphasis>test</emphasis> is something that
+      <emphasis>you</emphasis> run when <command role="hg-cmd">hg
+	bisect</command> chooses a changeset.  A
+      <emphasis>probe</emphasis> is what <command role="hg-cmd">hg
+	bisect</command> runs to tell whether a revision is good.
+      Finally, we'll use the word <quote>bisect</quote>, as both a
+      noun and a verb, to stand in for the phrase <quote>search using
+	the <command role="hg-cmd">hg bisect</command>
+	command</quote>.</para>
+
+    <para>One simple way to automate the searching process would be
+      simply to probe every changeset.  However, this scales poorly.
+      If it took ten minutes to test a single changeset, and you had
+      10,000 changesets in your repository, the exhaustive approach
+      would take on average 35 <emphasis>days</emphasis> to find the
+      changeset that introduced a bug.  Even if you knew that the bug
+      was introduced by one of the last 500 changesets, and limited
+      your search to those, you'd still be looking at over 40 hours to
+      find the changeset that introduced your bug.</para>
+
+    <para>What the <command role="hg-cmd">hg bisect</command> command
+      does is use its knowledge of the <quote>shape</quote> of your
+      project's revision history to perform a search in time
+      proportional to the <emphasis>logarithm</emphasis> of the number
+      of changesets to check (the kind of search it performs is called
+      a dichotomic search).  With this approach, searching through
+      10,000 changesets will take less than three hours, even at ten
+      minutes per test (the search will require about 14 tests).
+      Limit your search to the last hundred changesets, and it will
+      take only about an hour (roughly seven tests).</para>
+
+    <para>The <command role="hg-cmd">hg bisect</command> command is
+      aware of the <quote>branchy</quote> nature of a Mercurial
+      project's revision history, so it has no problems dealing with
+      branches, merges, or multiple heads in a repository.  It can
+      prune entire branches of history with a single probe, which is
+      how it operates so efficiently.</para>
+
+    <sect2>
+      <title>Using the <command role="hg-cmd">hg bisect</command>
+	command</title>
+
+      <para>Here's an example of <command role="hg-cmd">hg
+	  bisect</command> in action.</para>
+
+      <note>
+	<para>  In versions 0.9.5 and earlier of Mercurial, <command
+	    role="hg-cmd">hg bisect</command> was not a core command:
+	  it was distributed with Mercurial as an extension. This
+	  section describes the built-in command, not the old
+	  extension.</para>
+      </note>
+
+      <para>Now let's create a repository, so that we can try out the
+	<command role="hg-cmd">hg bisect</command> command in
+	isolation. <!-- &interaction.bisect.init; --> We'll simulate a
+	project that has a bug in it in a simple-minded way: create
+	trivial changes in a loop, and nominate one specific change
+	that will have the <quote>bug</quote>.  This loop creates 35
+	changesets, each adding a single file to the repository.
+	We'll represent our <quote>bug</quote> with a file that
+	contains the text <quote>i have a gub</quote>. <!--
+	&interaction.bisect.commits; --></para>
+
+      <para>The next thing that we'd like to do is figure out how to
+	use the <command role="hg-cmd">hg bisect</command> command.
+	We can use Mercurial's normal built-in help mechanism for
+	this. <!-- &interaction.bisect.help; --></para>
+
+      <para>The <command role="hg-cmd">hg bisect</command> command
+	works in steps.  Each step proceeds as follows.</para>
+      <orderedlist>
+	<listitem><para>You run your binary test.</para>
+	  <itemizedlist>
+	    <listitem><para>If the test succeeded, you tell <command
+		  role="hg-cmd">hg bisect</command> by running the
+		<command role="hg-cmd">hg bisect good</command>
+		command.</para>
+	    </listitem>
+	    <listitem><para>If it failed, run the <command
+		  role="hg-cmd">hg bisect bad</command>
+		command.</para></listitem></itemizedlist>
+	</listitem>
+	<listitem><para>The command uses your information to decide
+	    which changeset to test next.</para>
+	</listitem>
+	<listitem><para>It updates the working directory to that
+	    changeset, and the process begins again.</para>
+	</listitem></orderedlist>
+      <para>The process ends when <command role="hg-cmd">hg
+	  bisect</command> identifies a unique changeset that marks
+	the point where your test transitioned from
+	<quote>succeeding</quote> to <quote>failing</quote>.</para>
+
+      <para>To start the search, we must run the <command
+	  role="hg-cmd">hg bisect --reset</command> command. <!--
+	&interaction.bisect.search.init; --></para>
+
+      <para>In our case, the binary test we use is simple: we check to
+	see if any file in the repository contains the string <quote>i
+	  have a gub</quote>.  If it does, this changeset contains the
+	change that <quote>caused the bug</quote>.  By convention, a
+	changeset that has the property we're searching for is
+	<quote>bad</quote>, while one that doesn't is
+	<quote>good</quote>.</para>
+
+      <para>Most of the time, the revision to which the working
+	directory is synced (usually the tip) already exhibits the
+	problem introduced by the buggy change, so we'll mark it as
+	<quote>bad</quote>. <!-- &interaction.bisect.search.bad-init;
+	--></para>
+
+      <para>Our next task is to nominate a changeset that we know
+	<emphasis>doesn't</emphasis> have the bug; the <command
+	  role="hg-cmd">hg bisect</command> command will
+	<quote>bracket</quote> its search between the first pair of
+	good and bad changesets.  In our case, we know that revision
+	10 didn't have the bug.  (I'll have more words about choosing
+	the first <quote>good</quote> changeset later.) <!--
+	&interaction.bisect.search.good-init; --></para>
+
+      <para>Notice that this command printed some output.</para>
+      <itemizedlist>
+	<listitem><para>It told us how many changesets it must
+	    consider before it can identify the one that introduced
+	    the bug, and how many tests that will require.</para>
+	</listitem>
+	<listitem><para>It updated the working directory to the next
+	    changeset to test, and told us which changeset it's
+	    testing.</para>
+	</listitem></itemizedlist>
+
+      <para>We now run our test in the working directory.  We use the
+	<command>grep</command> command to see if our
+	<quote>bad</quote> file is present in the working directory.
+	If it is, this revision is bad; if not, this revision is good.
+	<!-- &interaction.bisect.search.step1; --></para>
+
+      <para>This test looks like a perfect candidate for automation,
+	so let's turn it into a shell function. <!--
+	&interaction.bisect.search.mytest; --> We can now run an
+	entire test step with a single command,
+	<literal>mytest</literal>. <!--
+	&interaction.bisect.search.step2; --> A few more invocations
+	of our canned test step command, and we're done. <!--
+	&interaction.bisect.search.rest; --></para>
+
+      <para>Even though we had 40 changesets to search through, the
+	<command role="hg-cmd">hg bisect</command> command let us find
+	the changeset that introduced our <quote>bug</quote> with only
+	five tests.  Because the number of tests that the <command
+	  role="hg-cmd">hg bisect</command> command performs grows
+	logarithmically with the number of changesets to search, the
+	advantage that it has over the <quote>brute force</quote>
+	search approach increases with every changeset you add.</para>
+
+    </sect2>
+    <sect2>
+      <title>Cleaning up after your search</title>
+
+      <para>When you're finished using the <command role="hg-cmd">hg
+	  bisect</command> command in a repository, you can use the
+	<command role="hg-cmd">hg bisect reset</command> command to
+	drop the information it was using to drive your search.  The
+	command doesn't use much space, so it doesn't matter if you
+	forget to run this command.  However, <command
+	  role="hg-cmd">hg bisect</command> won't let you start a new
+	search in that repository until you do a <command
+	  role="hg-cmd">hg bisect reset</command>. <!--
+	&interaction.bisect.search.reset; --></para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Tips for finding bugs effectively</title>
+
+    <sect2>
+      <title>Give consistent input</title>
+
+      <para>The <command role="hg-cmd">hg bisect</command> command
+	requires that you correctly report the result of every test
+	you perform.  If you tell it that a test failed when it really
+	succeeded, it <emphasis>might</emphasis> be able to detect the
+	inconsistency.  If it can identify an inconsistency in your
+	reports, it will tell you that a particular changeset is both
+	good and bad. However, it can't do this perfectly; it's about
+	as likely to report the wrong changeset as the source of the
+	bug.</para>
+
+    </sect2>
+    <sect2>
+      <title>Automate as much as possible</title>
+
+      <para>When I started using the <command role="hg-cmd">hg
+	  bisect</command> command, I tried a few times to run my
+	tests by hand, on the command line.  This is an approach that
+	I, at least, am not suited to.  After a few tries, I found
+	that I was making enough mistakes that I was having to restart
+	my searches several times before finally getting correct
+	results.</para>
+
+      <para>My initial problems with driving the <command
+	  role="hg-cmd">hg bisect</command> command by hand occurred
+	even with simple searches on small repositories; if the
+	problem you're looking for is more subtle, or the number of
+	tests that <command role="hg-cmd">hg bisect</command> must
+	perform increases, the likelihood of operator error ruining
+	the search is much higher.  Once I started automating my
+	tests, I had much better results.</para>
+
+      <para>The key to automated testing is twofold:</para>
+      <itemizedlist>
+	<listitem><para>always test for the same symptom, and</para>
+	</listitem>
+	<listitem><para>always feed consistent input to the <command
+	      role="hg-cmd">hg bisect</command> command.</para>
+	</listitem></itemizedlist>
+      <para>In my tutorial example above, the <command>grep</command>
+	command tests for the symptom, and the <literal>if</literal>
+	statement takes the result of this check and ensures that we
+	always feed the same input to the <command role="hg-cmd">hg
+	  bisect</command> command.  The <literal>mytest</literal>
+	function marries these together in a reproducible way, so that
+	every test is uniform and consistent.</para>
+
+    </sect2>
+    <sect2>
+      <title>Check your results</title>
+
+      <para>Because the output of a <command role="hg-cmd">hg
+	  bisect</command> search is only as good as the input you
+	give it, don't take the changeset it reports as the absolute
+	truth.  A simple way to cross-check its report is to manually
+	run your test at each of the following changesets:</para>
+      <itemizedlist>
+	<listitem><para>The changeset that it reports as the first bad
+	    revision.  Your test should still report this as
+	    bad.</para>
+	</listitem>
+	<listitem><para>The parent of that changeset (either parent,
+	    if it's a merge). Your test should report this changeset
+	    as good.</para>
+	</listitem>
+	<listitem><para>A child of that changeset.  Your test should
+	    report this changeset as bad.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title>Beware interference between bugs</title>
+
+      <para>It's possible that your search for one bug could be
+	disrupted by the presence of another.  For example, let's say
+	your software crashes at revision 100, and worked correctly at
+	revision 50.  Unknown to you, someone else introduced a
+	different crashing bug at revision 60, and fixed it at
+	revision 80.  This could distort your results in one of
+	several ways.</para>
+
+      <para>It is possible that this other bug completely
+	<quote>masks</quote> yours, which is to say that it occurs
+	before your bug has a chance to manifest itself.  If you can't
+	avoid that other bug (for example, it prevents your project
+	from building), and so can't tell whether your bug is present
+	in a particular changeset, the <command role="hg-cmd">hg
+	  bisect</command> command cannot help you directly.  Instead,
+	you can mark a changeset as untested by running <command
+	  role="hg-cmd">hg bisect --skip</command>.</para>
+
+      <para>A different problem could arise if your test for a bug's
+	presence is not specific enough.  If you check for <quote>my
+	  program crashes</quote>, then both your crashing bug and an
+	unrelated crashing bug that masks it will look like the same
+	thing, and mislead <command role="hg-cmd">hg
+	  bisect</command>.</para>
+
+      <para>Another useful situation in which to use <command
+	  role="hg-cmd">hg bisect --skip</command> is if you can't
+	test a revision because your project was in a broken and hence
+	untestable state at that revision, perhaps because someone
+	checked in a change that prevented the project from
+	building.</para>
+
+    </sect2>
+    <sect2>
+      <title>Bracket your search lazily</title>
+
+      <para>Choosing the first <quote>good</quote> and
+	<quote>bad</quote> changesets that will mark the end points of
+	your search is often easy, but it bears a little discussion
+	nevertheless.  From the perspective of <command
+	  role="hg-cmd">hg bisect</command>, the <quote>newest</quote>
+	changeset is conventionally <quote>bad</quote>, and the older
+	changeset is <quote>good</quote>.</para>
+
+      <para>If you're having trouble remembering when a suitable
+	<quote>good</quote> change was, so that you can tell <command
+	  role="hg-cmd">hg bisect</command>, you could do worse than
+	testing changesets at random.  Just remember to eliminate
+	contenders that can't possibly exhibit the bug (perhaps
+	because the feature with the bug isn't present yet) and those
+	where another problem masks the bug (as I discussed
+	above).</para>
+
+      <para>Even if you end up <quote>early</quote> by thousands of
+	changesets or months of history, you will only add a handful
+	of tests to the total number that <command role="hg-cmd">hg
+	  bisect</command> must perform, thanks to its logarithmic
+	behaviour.</para>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch10-hook.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch10-hook.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,2067 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:hook">
+  <title>Handling repository events with hooks</title>
+
+  <para>Mercurial offers a powerful mechanism to let you perform
+    automated actions in response to events that occur in a
+    repository.  In some cases, you can even control Mercurial's
+    response to those events.</para>
+
+  <para>The name Mercurial uses for one of these actions is a
+    <emphasis>hook</emphasis>. Hooks are called
+    <quote>triggers</quote> in some revision control systems, but the
+    two names refer to the same idea.</para>
+
+  <sect1>
+    <title>An overview of hooks in Mercurial</title>
+
+    <para>Here is a brief list of the hooks that Mercurial supports.
+      We will revisit each of these hooks in more detail later, in
+      section <xref linkend="sec:hook:ref"/>.</para>
+
+    <itemizedlist>
+      <listitem><para><literal role="hook">changegroup</literal>: This
+	  is run after a group of changesets has been brought into the
+	  repository from elsewhere.</para>
+      </listitem>
+      <listitem><para><literal role="hook">commit</literal>: This is
+	  run after a new changeset has been created in the local
+	  repository.</para>
+      </listitem>
+      <listitem><para><literal role="hook">incoming</literal>: This is
+	  run once for each new changeset that is brought into the
+	  repository from elsewhere.  Notice the difference from
+	  <literal role="hook">changegroup</literal>, which is run
+	  once per <emphasis>group</emphasis> of changesets brought
+	  in.</para>
+      </listitem>
+      <listitem><para><literal role="hook">outgoing</literal>: This is
+	  run after a group of changesets has been transmitted from
+	  this repository.</para>
+      </listitem>
+      <listitem><para><literal role="hook">prechangegroup</literal>:
+	  This is run before starting to bring a group of changesets
+	  into the repository.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">precommit</literal>:
+	  Controlling. This is run before starting a commit.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">preoutgoing</literal>:
+	  Controlling. This is run before starting to transmit a group
+	  of changesets from this repository.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">pretag</literal>:
+	  Controlling. This is run before creating a tag.
+	</para>
+      </listitem>
+      <listitem><para><literal
+	    role="hook">pretxnchangegroup</literal>: Controlling. This
+	  is run after a group of changesets has been brought into the
+	  local repository from another, but before the transaction
+	  completes that will make the changes permanent in the
+	  repository.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">pretxncommit</literal>:
+	  Controlling. This is run after a new changeset has been
+	  created in the local repository, but before the transaction
+	  completes that will make it permanent.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">preupdate</literal>:
+	  Controlling. This is run before starting an update or merge
+	  of the working directory.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">tag</literal>: This is run
+	  after a tag is created.
+	</para>
+      </listitem>
+      <listitem><para><literal role="hook">update</literal>: This is
+	  run after an update or merge of the working directory has
+	  finished.
+	</para>
+      </listitem></itemizedlist>
+    <para>Each of the hooks whose description begins with the word
+      <quote>Controlling</quote> has the ability to determine whether
+      an activity can proceed.  If the hook succeeds, the activity may
+      proceed; if it fails, the activity is either not permitted or
+      undone, depending on the hook.
+    </para>
+
+  </sect1>
+  <sect1>
+    <title>Hooks and security</title>
+
+    <sect2>
+      <title>Hooks are run with your privileges</title>
+
+      <para>When you run a Mercurial command in a repository, and the
+	command causes a hook to run, that hook runs on
+	<emphasis>your</emphasis> system, under
+	<emphasis>your</emphasis> user account, with
+	<emphasis>your</emphasis> privilege level.  Since hooks are
+	arbitrary pieces of executable code, you should treat them
+	with an appropriate level of suspicion.  Do not install a hook
+	unless you are confident that you know who created it and what
+	it does.
+      </para>
+
+      <para>In some cases, you may be exposed to hooks that you did
+	not install yourself.  If you work with Mercurial on an
+	unfamiliar system, Mercurial will run hooks defined in that
+	system's global <filename role="special"> /.hgrc</filename>\
+	file.
+      </para>
+
+      <para>If you are working with a repository owned by another
+	user, Mercurial can run hooks defined in that user's
+	repository, but it will still run them as <quote>you</quote>.
+	For example, if you <command role="hg-cmd">hg pull</command>
+	from that repository, and its <filename
+	  role="special">.hg/hgrc</filename> defines a local <literal
+	  role="hook">outgoing</literal> hook, that hook will run
+	under your user account, even though you don't own that
+	repository.
+      </para>
+
+      <note>
+	<para>  This only applies if you are pulling from a repository
+	  on a local or network filesystem.  If you're pulling over
+	  http or ssh, any <literal role="hook">outgoing</literal>
+	  hook will run under whatever account is executing the server
+	  process, on the server.
+	</para>
+      </note>
+
+      <para>XXX To see what hooks are defined in a repository, use the
+	<command role="hg-cmd">hg config hooks</command> command.  If
+	you are working in one repository, but talking to another that
+	you do not own (e.g. using <command role="hg-cmd">hg
+	  pull</command> or <command role="hg-cmd">hg
+	  incoming</command>), remember that it is the other
+	repository's hooks you should be checking, not your own.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Hooks do not propagate</title>
+
+      <para>In Mercurial, hooks are not revision controlled, and do
+	not propagate when you clone, or pull from, a repository.  The
+	reason for this is simple: a hook is a completely arbitrary
+	piece of executable code.  It runs under your user identity,
+	with your privilege level, on your machine.
+      </para>
+
+      <para>It would be extremely reckless for any distributed
+	revision control system to implement revision-controlled
+	hooks, as this would offer an easily exploitable way to
+	subvert the accounts of users of the revision control system.
+      </para>
+
+      <para>Since Mercurial does not propagate hooks, if you are
+	collaborating with other people on a common project, you
+	should not assume that they are using the same Mercurial hooks
+	as you are, or that theirs are correctly configured.  You
+	should document the hooks you expect people to use.
+      </para>
+
+      <para>In a corporate intranet, this is somewhat easier to
+	control, as you can for example provide a
+	<quote>standard</quote> installation of Mercurial on an NFS
+	filesystem, and use a site-wide <filename role="special">
+	  /.hgrc</filename>\ file to define hooks that all users will
+	see.  However, this too has its limits; see below.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Hooks can be overridden</title>
+
+      <para>Mercurial allows you to override a hook definition by
+	redefining the hook.  You can disable it by setting its value
+	to the empty string, or change its behaviour as you wish.
+      </para>
+
+      <para>If you deploy a system- or site-wide <filename
+	  role="special"> /.hgrc</filename>\ file that defines some
+	hooks, you should thus understand that your users can disable
+	or override those hooks.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Ensuring that critical hooks are run</title>
+
+      <para>Sometimes you may want to enforce a policy that you do not
+	want others to be able to work around.  For example, you may
+	have a requirement that every changeset must pass a rigorous
+	set of tests.  Defining this requirement via a hook in a
+	site-wide <filename role="special"> /.hgrc</filename>\ won't
+	work for remote users on laptops, and of course local users
+	can subvert it at will by overriding the hook.
+      </para>
+
+      <para>Instead, you can set up your policies for use of Mercurial
+	so that people are expected to propagate changes through a
+	well-known <quote>canonical</quote> server that you have
+	locked down and configured appropriately.
+      </para>
+
+      <para>One way to do this is via a combination of social
+	engineering and technology.  Set up a restricted-access
+	account; users can push changes over the network to
+	repositories managed by this account, but they cannot log into
+	the account and run normal shell commands.  In this scenario,
+	a user can commit a changeset that contains any old garbage
+	they want.
+      </para>
+
+      <para>When someone pushes a changeset to the server that
+	everyone pulls from, the server will test the changeset before
+	it accepts it as permanent, and reject it if it fails to pass
+	the test suite.  If people only pull changes from this
+	filtering server, it will serve to ensure that all changes
+	that people pull have been automatically vetted.
+      </para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Care with <literal>pretxn</literal> hooks in a
+      shared-access repository</title>
+
+    <para>If you want to use hooks to do some automated work in a
+      repository that a number of people have shared access to, you
+      need to be careful in how you do this.
+    </para>
+
+    <para>Mercurial only locks a repository when it is writing to the
+      repository, and only the parts of Mercurial that write to the
+      repository pay attention to locks.  Write locks are necessary to
+      prevent multiple simultaneous writers from scribbling on each
+      other's work, corrupting the repository.
+    </para>
+
+    <para>Because Mercurial is careful with the order in which it
+      reads and writes data, it does not need to acquire a lock when
+      it wants to read data from the repository.  The parts of
+      Mercurial that read from the repository never pay attention to
+      locks.  This lockless reading scheme greatly increases
+      performance and concurrency.
+    </para>
+
+    <para>With great performance comes a trade-off, though, one which
+      has the potential to cause you trouble unless you're aware of
+      it.  To describe this requires a little detail about how
+      Mercurial adds changesets to a repository and reads those
+      changes.
+    </para>
+
+    <para>When Mercurial <emphasis>writes</emphasis> metadata, it
+      writes it straight into the destination file.  It writes file
+      data first, then manifest data (which contains pointers to the
+      new file data), then changelog data (which contains pointers to
+      the new manifest data).  Before the first write to each file, it
+      stores a record of where the end of the file was in its
+      transaction log.  If the transaction must be rolled back,
+      Mercurial simply truncates each file back to the size it was
+      before the transaction began.
+    </para>
+
+    <para>When Mercurial <emphasis>reads</emphasis> metadata, it reads
+      the changelog first, then everything else.  Since a reader will
+      only access parts of the manifest or file metadata that it can
+      see in the changelog, it can never see partially written data.
+    </para>
+
+    <para>Some controlling hooks (<literal
+	role="hook">pretxncommit</literal> and <literal
+	role="hook">pretxnchangegroup</literal>) run when a
+      transaction is almost complete. All of the metadata has been
+      written, but Mercurial can still roll the transaction back and
+      cause the newly-written data to disappear.
+    </para>
+
+    <para>If one of these hooks runs for long, it opens a window of
+      time during which a reader can see the metadata for changesets
+      that are not yet permanent, and should not be thought of as
+      <quote>really there</quote>.  The longer the hook runs, the
+      longer that window is open.
+    </para>
+
+    <sect2>
+      <title>The problem illustrated</title>
+
+      <para>In principle, a good use for the <literal
+	  role="hook">pretxnchangegroup</literal> hook would be to
+	automatically build and test incoming changes before they are
+	accepted into a central repository.  This could let you
+	guarantee that nobody can push changes to this repository that
+	<quote>break the build</quote>. But if a client can pull
+	changes while they're being tested, the usefulness of the test
+	is zero; an unsuspecting someone can pull untested changes,
+	potentially breaking their build.
+      </para>
+
+      <para>The safest technological answer to this challenge is to
+	set up such a <quote>gatekeeper</quote> repository as
+	<emphasis>unidirectional</emphasis>.  Let it take changes
+	pushed in from the outside, but do not allow anyone to pull
+	changes from it (use the <literal
+	  role="hook">preoutgoing</literal> hook to lock it down).
+	Configure a <literal role="hook">changegroup</literal> hook so
+	that if a build or test succeeds, the hook will push the new
+	changes out to another repository that people
+	<emphasis>can</emphasis> pull from.
+      </para>
+
+      <para>In practice, putting a centralised bottleneck like this in
+	place is not often a good idea, and transaction visibility has
+	nothing to do with the problem.  As the size of a
+	project&emdash;and the time it takes to build and
+	test&emdash;grows, you rapidly run into a wall with this
+	<quote>try before you buy</quote> approach, where you have
+	more changesets to test than time in which to deal with them.
+	The inevitable result is frustration on the part of all
+	involved.
+      </para>
+
+      <para>An approach that scales better is to get people to build
+	and test before they push, then run automated builds and tests
+	centrally <emphasis>after</emphasis> a push, to be sure all is
+	well.  The advantage of this approach is that it does not
+	impose a limit on the rate at which the repository can accept
+	changes.
+      </para>
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:hook:simple">
+    <title>A short tutorial on using hooks</title>
+
+    <para>It is easy to write a Mercurial hook.  Let's start with a
+      hook that runs when you finish a <command role="hg-cmd">hg
+	commit</command>, and simply prints the hash of the changeset
+      you just created.  The hook is called <literal
+	role="hook">commit</literal>.
+    </para>
+
+    <para>All hooks follow the pattern in this example.</para>
+
+<!-- &interaction.hook.simple.init; -->
+
+    <para>You add an entry to the <literal
+	role="rc-hooks">hooks</literal> section of your <filename
+	role="special"> /.hgrc</filename>.  On the left is the name of
+      the event to trigger on; on the right is the action to take.  As
+      you can see, you can run an arbitrary shell command in a hook.
+      Mercurial passes extra information to the hook using environment
+      variables (look for <envar>HG_NODE</envar> in the example).
+    </para>
+
+    <sect2>
+      <title>Performing multiple actions per event</title>
+
+      <para>Quite often, you will want to define more than one hook
+	for a particular kind of event, as shown below.</para>
+
+<!-- &interaction.hook.simple.ext; -->
+
+      <para>Mercurial lets you do this by adding an
+	<emphasis>extension</emphasis> to the end of a hook's name.
+	You extend a hook's name by giving the name of the hook,
+	followed by a full stop (the
+	<quote><literal>.</literal></quote> character), followed by
+	some more text of your choosing.  For example, Mercurial will
+	run both <literal>commit.foo</literal> and
+	<literal>commit.bar</literal> when the
+	<literal>commit</literal> event occurs.
+      </para>
+
+      <para>To give a well-defined order of execution when there are
+	multiple hooks defined for an event, Mercurial sorts hooks by
+	extension, and executes the hook commands in this sorted
+	order.  In the above example, it will execute
+	<literal>commit.bar</literal> before
+	<literal>commit.foo</literal>, and <literal>commit</literal>
+	before both.
+      </para>
+
+      <para>It is a good idea to use a somewhat descriptive extension
+	when you define a new hook.  This will help you to remember
+	what the hook was for.  If the hook fails, you'll get an error
+	message that contains the hook name and extension, so using a
+	descriptive extension could give you an immediate hint as to
+	why the hook failed (see section <xref
+	  linkend="sec:hook:perm"/> for an example).
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:perm">
+      <title>Controlling whether an activity can proceed</title>
+
+      <para>In our earlier examples, we used the <literal
+	  role="hook">commit</literal> hook, which is run after a
+	commit has completed.  This is one of several Mercurial hooks
+	that run after an activity finishes.  Such hooks have no way
+	of influencing the activity itself.
+      </para>
+
+      <para>Mercurial defines a number of events that occur before an
+	activity starts; or after it starts, but before it finishes.
+	Hooks that trigger on these events have the added ability to
+	choose whether the activity can continue, or will abort.
+      </para>
+
+      <para>The <literal role="hook">pretxncommit</literal> hook runs
+	after a commit has all but completed.  In other words, the
+	metadata representing the changeset has been written out to
+	disk, but the transaction has not yet been allowed to
+	complete.  The <literal role="hook">pretxncommit</literal>
+	hook has the ability to decide whether the transaction can
+	complete, or must be rolled back.
+      </para>
+
+      <para>If the <literal role="hook">pretxncommit</literal> hook
+	exits with a status code of zero, the transaction is allowed
+	to complete; the commit finishes; and the <literal
+	  role="hook">commit</literal> hook is run.  If the <literal
+	  role="hook">pretxncommit</literal> hook exits with a
+	non-zero status code, the transaction is rolled back; the
+	metadata representing the changeset is erased; and the
+	<literal role="hook">commit</literal> hook is not run.
+      </para>
+
+<!-- &interaction.hook.simple.pretxncommit; -->
+
+      <para>The hook in the example above checks that a commit comment
+	contains a bug ID.  If it does, the commit can complete.  If
+	not, the commit is rolled back.
+      </para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Writing your own hooks</title>
+
+    <para>When you are writing a hook, you might find it useful to run
+      Mercurial either with the <option
+	role="hg-opt-global">-v</option> option, or the <envar
+	role="rc-item-ui">verbose</envar> config item set to
+      <quote>true</quote>.  When you do so, Mercurial will print a
+      message before it calls each hook.
+    </para>
+
+    <sect2 id="sec:hook:lang">
+      <title>Choosing how your hook should run</title>
+
+      <para>You can write a hook either as a normal
+	program&emdash;typically a shell script&emdash;or as a Python
+	function that is executed within the Mercurial process.
+      </para>
+
+      <para>Writing a hook as an external program has the advantage
+	that it requires no knowledge of Mercurial's internals.  You
+	can call normal Mercurial commands to get any added
+	information you need.  The trade-off is that external hooks
+	are slower than in-process hooks.
+      </para>
+
+      <para>An in-process Python hook has complete access to the
+	Mercurial API, and does not <quote>shell out</quote> to
+	another process, so it is inherently faster than an external
+	hook.  It is also easier to obtain much of the information
+	that a hook requires by using the Mercurial API than by
+	running Mercurial commands.
+      </para>
+
+      <para>If you are comfortable with Python, or require high
+	performance, writing your hooks in Python may be a good
+	choice.  However, when you have a straightforward hook to
+	write and you don't need to care about performance (probably
+	the majority of hooks), a shell script is perfectly fine.
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:param">
+      <title>Hook parameters</title>
+
+      <para>Mercurial calls each hook with a set of well-defined
+	parameters.  In Python, a parameter is passed as a keyword
+	argument to your hook function.  For an external program, a
+	parameter is passed as an environment variable.
+      </para>
+
+      <para>Whether your hook is written in Python or as a shell
+	script, the hook-specific parameter names and values will be
+	the same.  A boolean parameter will be represented as a
+	boolean value in Python, but as the number 1 (for
+	<quote>true</quote>) or 0 (for <quote>false</quote>) as an
+	environment variable for an external hook.  If a hook
+	parameter is named <literal>foo</literal>, the keyword
+	argument for a Python hook will also be named
+	<literal>foo</literal>, while the environment variable for an
+	external hook will be named <literal>HG_FOO</literal>.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Hook return values and activity control</title>
+
+      <para>A hook that executes successfully must exit with a status
+	of zero if external, or return boolean <quote>false</quote> if
+	in-process.  Failure is indicated with a non-zero exit status
+	from an external hook, or an in-process hook returning boolean
+	<quote>true</quote>.  If an in-process hook raises an
+	exception, the hook is considered to have failed.
+      </para>
+
+      <para>For a hook that controls whether an activity can proceed,
+	zero/false means <quote>allow</quote>, while
+	non-zero/true/exception means <quote>deny</quote>.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Writing an external hook</title>
+
+      <para>When you define an external hook in your <filename
+	  role="special"> /.hgrc</filename>\ and the hook is run, its
+	value is passed to your shell, which interprets it.  This
+	means that you can use normal shell constructs in the body of
+	the hook.
+      </para>
+
+      <para>An executable hook is always run with its current
+	directory set to a repository's root directory.
+      </para>
+
+      <para>Each hook parameter is passed in as an environment
+	variable; the name is upper-cased, and prefixed with the
+	string <quote><literal>HG_</literal></quote>.
+      </para>
+
+      <para>With the exception of hook parameters, Mercurial does not
+	set or modify any environment variables when running a hook.
+	This is useful to remember if you are writing a site-wide hook
+	that may be run by a number of different users with differing
+	environment variables set. In multi-user situations, you
+	should not rely on environment variables being set to the
+	values you have in your environment when testing the hook.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Telling Mercurial to use an in-process hook</title>
+
+      <para>The <filename role="special"> /.hgrc</filename>\ syntax
+	for defining an in-process hook is slightly different than for
+	an executable hook.  The value of the hook must start with the
+	text <quote><literal>python:</literal></quote>, and continue
+	with the fully-qualified name of a callable object to use as
+	the hook's value.
+      </para>
+
+      <para>The module in which a hook lives is automatically imported
+	when a hook is run.  So long as you have the module name and
+	<envar>PYTHONPATH</envar> right, it should <quote>just
+	  work</quote>.
+      </para>
+
+      <para>The following <filename role="special"> /.hgrc</filename>\
+	example snippet illustrates the syntax and meaning of the
+	notions we just described.
+      </para>
+      <programlisting>[hooks] commit.example =
+	python:mymodule.submodule.myhook</programlisting>
+      <para>When Mercurial runs the <literal>commit.example</literal>
+	hook, it imports <literal>mymodule.submodule</literal>, looks
+	for the callable object named <literal>myhook</literal>, and
+	calls it.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Writing an in-process hook</title>
+
+      <para>The simplest in-process hook does nothing, but illustrates
+	the basic shape of the hook API:
+      </para>
+      <programlisting>def myhook(ui, repo, **kwargs):
+	pass</programlisting>
+      <para>The first argument to a Python hook is always a <literal
+	  role="py-mod-mercurial.ui">ui</literal> object.  The second
+	is a repository object; at the moment, it is always an
+	instance of <literal
+	  role="py-mod-mercurial.localrepo">localrepository</literal>.
+	Following these two arguments are other keyword arguments.
+	Which ones are passed in depends on the hook being called, but
+	a hook can ignore arguments it doesn't care about by dropping
+	them into a keyword argument dict, as with
+	<literal>**kwargs</literal> above.
+      </para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Some hook examples</title>
+
+    <sect2>
+      <title>Writing meaningful commit messages</title>
+
+      <para>It's hard to imagine a useful commit message being very
+	short. The simple <literal role="hook">pretxncommit</literal>
+	hook of the example below will prevent you from committing a
+	changeset with a message that is less than ten bytes long.
+      </para>
+
+<!-- &interaction.hook.msglen.go; -->
+
+    </sect2>
+    <sect2>
+      <title>Checking for trailing whitespace</title>
+
+      <para>An interesting use of a commit-related hook is to help you
+	to write cleaner code.  A simple example of <quote>cleaner
+	  code</quote> is the dictum that a change should not add any
+	new lines of text that contain <quote>trailing
+	  whitespace</quote>.  Trailing whitespace is a series of
+	space and tab characters at the end of a line of text.  In
+	most cases, trailing whitespace is unnecessary, invisible
+	noise, but it is occasionally problematic, and people often
+	prefer to get rid of it.
+      </para>
+
+      <para>You can use either the <literal
+	  role="hook">precommit</literal> or <literal
+	  role="hook">pretxncommit</literal> hook to tell whether you
+	have a trailing whitespace problem.  If you use the <literal
+	  role="hook">precommit</literal> hook, the hook will not know
+	which files you are committing, so it will have to check every
+	modified file in the repository for trailing white space.  If
+	you want to commit a change to just the file
+	<filename>foo</filename>, but the file
+	<filename>bar</filename> contains trailing whitespace, doing a
+	check in the <literal role="hook">precommit</literal> hook
+	will prevent you from committing <filename>foo</filename> due
+	to the problem with <filename>bar</filename>.  This doesn't
+	seem right.
+      </para>
+
+      <para>Should you choose the <literal
+	  role="hook">pretxncommit</literal> hook, the check won't
+	occur until just before the transaction for the commit
+	completes.  This will allow you to check for problems only the
+	exact files that are being committed.  However, if you entered
+	the commit message interactively and the hook fails, the
+	transaction will roll back; you'll have to re-enter the commit
+	message after you fix the trailing whitespace and run <command
+	  role="hg-cmd">hg commit</command> again.
+      </para>
+
+<!-- &interaction.hook.ws.simple; -->
+
+      <para>In this example, we introduce a simple <literal
+	  role="hook">pretxncommit</literal> hook that checks for
+	trailing whitespace.  This hook is short, but not very
+	helpful.  It exits with an error status if a change adds a
+	line with trailing whitespace to any file, but does not print
+	any information that might help us to identify the offending
+	file or line.  It also has the nice property of not paying
+	attention to unmodified lines; only lines that introduce new
+	trailing whitespace cause problems.
+      </para>
+
+      <para>The above version is much more complex, but also more
+	useful.  It parses a unified diff to see if any lines add
+	trailing whitespace, and prints the name of the file and the
+	line number of each such occurrence.  Even better, if the
+	change adds trailing whitespace, this hook saves the commit
+	comment and prints the name of the save file before exiting
+	and telling Mercurial to roll the transaction back, so you can
+	use the <option role="hg-opt-commit">-l filename</option>
+	option to <command role="hg-cmd">hg commit</command> to reuse
+	the saved commit message once you've corrected the problem.
+      </para>
+
+<!-- &interaction.hook.ws.better; -->
+
+      <para>As a final aside, note in the example above the use of
+	<command>perl</command>'s in-place editing feature to get rid
+	of trailing whitespace from a file.  This is concise and
+	useful enough that I will reproduce it here.
+      </para>
+      <programlisting>perl -pi -e 's,\s+$,,' filename</programlisting>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Bundled hooks</title>
+
+    <para>Mercurial ships with several bundled hooks.  You can find
+      them in the <filename class="directory">hgext</filename>
+      directory of a Mercurial source tree.  If you are using a
+      Mercurial binary package, the hooks will be located in the
+      <filename class="directory">hgext</filename> directory of
+      wherever your package installer put Mercurial.
+    </para>
+
+    <sect2>
+      <title><literal role="hg-ext">acl</literal>&emdash;access
+	control for parts of a repository</title>
+
+      <para>The <literal role="hg-ext">acl</literal> extension lets
+	you control which remote users are allowed to push changesets
+	to a networked server.  You can protect any portion of a
+	repository (including the entire repo), so that a specific
+	remote user can push changes that do not affect the protected
+	portion.
+      </para>
+
+      <para>This extension implements access control based on the
+	identity of the user performing a push,
+	<emphasis>not</emphasis> on who committed the changesets
+	they're pushing.  It makes sense to use this hook only if you
+	have a locked-down server environment that authenticates
+	remote users, and you want to be sure that only specific users
+	are allowed to push changes to that server.
+      </para>
+
+      <sect3>
+	<title>Configuring the <literal role="hook">acl</literal>
+	  hook</title>
+
+	<para>In order to manage incoming changesets, the <literal
+	    role="hg-ext">acl</literal> hook must be used as a
+	  <literal role="hook">pretxnchangegroup</literal> hook.  This
+	  lets it see which files are modified by each incoming
+	  changeset, and roll back a group of changesets if they
+	  modify <quote>forbidden</quote> files.  Example:
+	</para>
+	<programlisting>[hooks] pretxnchangegroup.acl =
+	  python:hgext.acl.hook</programlisting>
+
+	<para>The <literal role="hg-ext">acl</literal> extension is
+	  configured using three sections.
+	</para>
+
+	<para>The <literal role="rc-acl">acl</literal> section has
+	  only one entry, <envar role="rc-item-acl">sources</envar>,
+	  which lists the sources of incoming changesets that the hook
+	  should pay attention to.  You don't normally need to
+	  configure this section.
+	</para>
+	<itemizedlist>
+	  <listitem><para><envar role="rc-item-acl">serve</envar>:
+	      Control incoming changesets that are arriving from a
+	      remote repository over http or ssh.  This is the default
+	      value of <envar role="rc-item-acl">sources</envar>, and
+	      usually the only setting you'll need for this
+	      configuration item.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-acl">pull</envar>:
+	      Control incoming changesets that are arriving via a pull
+	      from a local repository.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-acl">push</envar>:
+	      Control incoming changesets that are arriving via a push
+	      from a local repository.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-acl">bundle</envar>:
+	      Control incoming changesets that are arriving from
+	      another repository via a bundle.
+	    </para>
+	  </listitem></itemizedlist>
+
+	<para>The <literal role="rc-acl.allow">acl.allow</literal>
+	  section controls the users that are allowed to add
+	  changesets to the repository.  If this section is not
+	  present, all users that are not explicitly denied are
+	  allowed.  If this section is present, all users that are not
+	  explicitly allowed are denied (so an empty section means
+	  that all users are denied).
+	</para>
+
+	<para>The <literal role="rc-acl.deny">acl.deny</literal>
+	  section determines which users are denied from adding
+	  changesets to the repository.  If this section is not
+	  present or is empty, no users are denied.
+	</para>
+
+	<para>The syntaxes for the <literal
+	    role="rc-acl.allow">acl.allow</literal> and <literal
+	    role="rc-acl.deny">acl.deny</literal> sections are
+	  identical.  On the left of each entry is a glob pattern that
+	  matches files or directories, relative to the root of the
+	  repository; on the right, a user name.
+	</para>
+
+	<para>In the following example, the user
+	  <literal>docwriter</literal> can only push changes to the
+	  <filename class="directory">docs</filename> subtree of the
+	  repository, while <literal>intern</literal> can push changes
+	  to any file or directory except <filename
+	    class="directory">source/sensitive</filename>.
+	</para>
+	<programlisting>[acl.allow] docs/** = docwriter [acl.deny]
+	  source/sensitive/** = intern</programlisting>
+
+      </sect3>
+      <sect3>
+	<title>Testing and troubleshooting</title>
+
+	<para>If you want to test the <literal
+	    role="hg-ext">acl</literal> hook, run it with Mercurial's
+	  debugging output enabled.  Since you'll probably be running
+	  it on a server where it's not convenient (or sometimes
+	  possible) to pass in the <option
+	    role="hg-opt-global">--debug</option> option, don't forget
+	  that you can enable debugging output in your <filename
+	    role="special"> /.hgrc</filename>:
+	</para>
+	<programlisting>[ui] debug = true</programlisting>
+	<para>With this enabled, the <literal
+	    role="hg-ext">acl</literal> hook will print enough
+	  information to let you figure out why it is allowing or
+	  forbidding pushes from specific users.
+	</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title><literal
+	  role="hg-ext">bugzilla</literal>&emdash;integration with
+	Bugzilla</title>
+
+      <para>The <literal role="hg-ext">bugzilla</literal> extension
+	adds a comment to a Bugzilla bug whenever it finds a reference
+	to that bug ID in a commit comment.  You can install this hook
+	on a shared server, so that any time a remote user pushes
+	changes to this server, the hook gets run.
+      </para>
+
+      <para>It adds a comment to the bug that looks like this (you can
+	configure the contents of the comment&emdash;see below):
+      </para>
+      <programlisting>Changeset aad8b264143a, made by Joe User
+	&lt;joe.user@domain.com&gt; in the frobnitz repository, refers
+	to this bug. For complete details, see
+	http://hg.domain.com/frobnitz?cmd=changeset;node=aad8b264143a
+	Changeset description: Fix bug 10483 by guarding against some
+	NULL pointers</programlisting>
+      <para>The value of this hook is that it automates the process of
+	updating a bug any time a changeset refers to it.  If you
+	configure the hook properly, it makes it easy for people to
+	browse straight from a Bugzilla bug to a changeset that refers
+	to that bug.
+      </para>
+
+      <para>You can use the code in this hook as a starting point for
+	some more exotic Bugzilla integration recipes.  Here are a few
+	possibilities:
+      </para>
+      <itemizedlist>
+	<listitem><para>Require that every changeset pushed to the
+	    server have a valid bug ID in its commit comment.  In this
+	    case, you'd want to configure the hook as a <literal
+	      role="hook">pretxncommit</literal> hook.  This would
+	    allow the hook to reject changes that didn't contain bug
+	    IDs.
+	  </para>
+	</listitem>
+	<listitem><para>Allow incoming changesets to automatically
+	    modify the <emphasis>state</emphasis> of a bug, as well as
+	    simply adding a comment.  For example, the hook could
+	    recognise the string <quote>fixed bug 31337</quote> as
+	    indicating that it should update the state of bug 31337 to
+	    <quote>requires testing</quote>.
+	  </para>
+	</listitem></itemizedlist>
+
+      <sect3 id="sec:hook:bugzilla:config">
+	<title>Configuring the <literal role="hook">bugzilla</literal>
+	  hook</title>
+
+	<para>You should configure this hook in your server's
+	  <filename role="special"> /.hgrc</filename>\ as an <literal
+	    role="hook">incoming</literal> hook, for example as
+	  follows:
+	</para>
+	<programlisting>[hooks] incoming.bugzilla =
+	  python:hgext.bugzilla.hook</programlisting>
+
+	<para>Because of the specialised nature of this hook, and
+	  because Bugzilla was not written with this kind of
+	  integration in mind, configuring this hook is a somewhat
+	  involved process.
+	</para>
+
+	<para>Before you begin, you must install the MySQL bindings
+	  for Python on the host(s) where you'll be running the hook.
+	  If this is not available as a binary package for your
+	  system, you can download it from
+	  <citation>web:mysql-python</citation>.
+	</para>
+
+	<para>Configuration information for this hook lives in the
+	  <literal role="rc-bugzilla">bugzilla</literal> section of
+	  your <filename role="special"> /.hgrc</filename>.
+	</para>
+	<itemizedlist>
+	  <listitem><para><envar
+		role="rc-item-bugzilla">version</envar>: The version
+	      of Bugzilla installed on the server.  The database
+	      schema that Bugzilla uses changes occasionally, so this
+	      hook has to know exactly which schema to use. At the
+	      moment, the only version supported is
+	      <literal>2.16</literal>.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-bugzilla">host</envar>:
+	      The hostname of the MySQL server that stores your
+	      Bugzilla data.  The database must be configured to allow
+	      connections from whatever host you are running the
+	      <literal role="hook">bugzilla</literal> hook on.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-bugzilla">user</envar>:
+	      The username with which to connect to the MySQL server.
+	      The database must be configured to allow this user to
+	      connect from whatever host you are running the <literal
+		role="hook">bugzilla</literal> hook on.  This user
+	      must be able to access and modify Bugzilla tables.  The
+	      default value of this item is <literal>bugs</literal>,
+	      which is the standard name of the Bugzilla user in a
+	      MySQL database.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar
+		role="rc-item-bugzilla">password</envar>: The MySQL
+	      password for the user you configured above.  This is
+	      stored as plain text, so you should make sure that
+	      unauthorised users cannot read the <filename
+		role="special"> /.hgrc</filename>\ file where you
+	      store this information.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-bugzilla">db</envar>:
+	      The name of the Bugzilla database on the MySQL server.
+	      The default value of this item is
+	      <literal>bugs</literal>, which is the standard name of
+	      the MySQL database where Bugzilla stores its data.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar
+		role="rc-item-bugzilla">notify</envar>: If you want
+	      Bugzilla to send out a notification email to subscribers
+	      after this hook has added a comment to a bug, you will
+	      need this hook to run a command whenever it updates the
+	      database.  The command to run depends on where you have
+	      installed Bugzilla, but it will typically look something
+	      like this, if you have Bugzilla installed in <filename
+		class="directory">/var/www/html/bugzilla</filename>:
+	    </para>
+	    <programlisting>cd /var/www/html/bugzilla &amp;&amp;
+	      ./processmail %s nobody@nowhere.com</programlisting>
+	  </listitem>
+	  <listitem><para>  The Bugzilla
+	      <literal>processmail</literal> program expects to be
+	      given a bug ID (the hook replaces
+	      <quote><literal>%s</literal></quote> with the bug ID)
+	      and an email address.  It also expects to be able to
+	      write to some files in the directory that it runs in.
+	      If Bugzilla and this hook are not installed on the same
+	      machine, you will need to find a way to run
+	      <literal>processmail</literal> on the server where
+	      Bugzilla is installed.
+	    </para>
+	  </listitem></itemizedlist>
+
+      </sect3>
+      <sect3>
+	<title>Mapping committer names to Bugzilla user names</title>
+
+	<para>By default, the <literal
+	    role="hg-ext">bugzilla</literal> hook tries to use the
+	  email address of a changeset's committer as the Bugzilla
+	  user name with which to update a bug.  If this does not suit
+	  your needs, you can map committer email addresses to
+	  Bugzilla user names using a <literal
+	    role="rc-usermap">usermap</literal> section.
+	</para>
+
+	<para>Each item in the <literal
+	    role="rc-usermap">usermap</literal> section contains an
+	  email address on the left, and a Bugzilla user name on the
+	  right.
+	</para>
+	<programlisting>[usermap] jane.user@example.com =
+	  jane</programlisting>
+	<para>You can either keep the <literal
+	    role="rc-usermap">usermap</literal> data in a normal
+	  <filename role="special">~/.hgrc</filename>, or tell the
+	  <literal role="hg-ext">bugzilla</literal> hook to read the
+	  information from an external <filename>usermap</filename>
+	  file.  In the latter case, you can store
+	  <filename>usermap</filename> data by itself in (for example)
+	  a user-modifiable repository.  This makes it possible to let
+	  your users maintain their own <envar
+	    role="rc-item-bugzilla">usermap</envar> entries.  The main
+	  <filename role="special"> /.hgrc</filename>\ file might look
+	  like this:
+	</para>
+	<programlisting># regular hgrc file refers to external usermap
+	  file [bugzilla] usermap =
+	  /home/hg/repos/userdata/bugzilla-usermap.conf</programlisting>
+	<para>While the <filename>usermap</filename> file that it
+	  refers to might look like this:
+	</para>
+	<programlisting># bugzilla-usermap.conf - inside a hg
+	  repository [usermap] stephanie@example.com =
+	  steph</programlisting>
+
+      </sect3>
+      <sect3>
+	<title>Configuring the text that gets added to a bug</title>
+
+	<para>You can configure the text that this hook adds as a
+	  comment; you specify it in the form of a Mercurial template.
+	  Several <filename role="special"> /.hgrc</filename>\ entries
+	  (still in the <literal role="rc-bugzilla">bugzilla</literal>
+	  section) control this behaviour.
+	</para>
+	<itemizedlist>
+	  <listitem><para><literal>strip</literal>: The number of
+	      leading path elements to strip from a repository's path
+	      name to construct a partial path for a URL. For example,
+	      if the repositories on your server live under <filename
+		class="directory">/home/hg/repos</filename>, and you
+	      have a repository whose path is <filename
+		class="directory">/home/hg/repos/app/tests</filename>,
+	      then setting <literal>strip</literal> to
+	      <literal>4</literal> will give a partial path of
+	      <filename class="directory">app/tests</filename>.  The
+	      hook will make this partial path available when
+	      expanding a template, as <literal>webroot</literal>.
+	    </para>
+	  </listitem>
+	  <listitem><para><literal>template</literal>: The text of the
+	      template to use.  In addition to the usual
+	      changeset-related variables, this template can use
+	      <literal>hgweb</literal> (the value of the
+	      <literal>hgweb</literal> configuration item above) and
+	      <literal>webroot</literal> (the path constructed using
+	      <literal>strip</literal> above).
+	    </para>
+	  </listitem></itemizedlist>
+
+	<para>In addition, you can add a <envar
+	    role="rc-item-web">baseurl</envar> item to the <literal
+	    role="rc-web">web</literal> section of your <filename
+	    role="special"> /.hgrc</filename>.  The <literal
+	    role="hg-ext">bugzilla</literal> hook will make this
+	  available when expanding a template, as the base string to
+	  use when constructing a URL that will let users browse from
+	  a Bugzilla comment to view a changeset.  Example:
+	</para>
+	<programlisting>[web] baseurl =
+	  http://hg.domain.com/</programlisting>
+
+	<para>Here is an example set of <literal
+	    role="hg-ext">bugzilla</literal> hook config information.
+	</para>
+	<programlisting>[bugzilla] host = bugzilla.example.com
+	  password = mypassword version = 2.16 # server-side repos
+	  live in /home/hg/repos, so strip 4 leading # separators
+	  strip = 4 hgweb = http://hg.example.com/ usermap =
+	  /home/hg/repos/notify/bugzilla.conf template = Changeset
+	  {node|short}, made by {author} in the {webroot} repo, refers
+	  to this bug.\\nFor complete details, see
+	  {hgweb}{webroot}?cmd=changeset;node={node|short}\\nChangeset
+	  description:\\n\\t{desc|tabindent}</programlisting>
+
+      </sect3>
+      <sect3>
+	<title>Testing and troubleshooting</title>
+
+	<para>The most common problems with configuring the <literal
+	    role="hg-ext">bugzilla</literal> hook relate to running
+	  Bugzilla's <filename>processmail</filename> script and
+	  mapping committer names to user names.
+	</para>
+
+	<para>Recall from section <xref
+	    linkend="sec:hook:bugzilla:config"/> above that the user
+	  that runs the Mercurial process on the server is also the
+	  one that will run the <filename>processmail</filename>
+	  script.  The <filename>processmail</filename> script
+	  sometimes causes Bugzilla to write to files in its
+	  configuration directory, and Bugzilla's configuration files
+	  are usually owned by the user that your web server runs
+	  under.
+	</para>
+
+	<para>You can cause <filename>processmail</filename> to be run
+	  with the suitable user's identity using the
+	  <command>sudo</command> command.  Here is an example entry
+	  for a <filename>sudoers</filename> file.
+	</para>
+	<programlisting>hg_user = (httpd_user) NOPASSWD:
+	  /var/www/html/bugzilla/processmail-wrapper
+	  %s</programlisting>
+	<para>This allows the <literal>hg_user</literal> user to run a
+	  <filename>processmail-wrapper</filename> program under the
+	  identity of <literal>httpd_user</literal>.
+	</para>
+
+	<para>This indirection through a wrapper script is necessary,
+	  because <filename>processmail</filename> expects to be run
+	  with its current directory set to wherever you installed
+	  Bugzilla; you can't specify that kind of constraint in a
+	  <filename>sudoers</filename> file.  The contents of the
+	  wrapper script are simple:
+	</para>
+	<programlisting>#!/bin/sh cd `dirname $0` &amp;&amp;
+	  ./processmail "$1" nobody@example.com</programlisting>
+	<para>It doesn't seem to matter what email address you pass to
+	  <filename>processmail</filename>.
+	</para>
+
+	<para>If your <literal role="rc-usermap">usermap</literal> is
+	  not set up correctly, users will see an error message from
+	  the <literal role="hg-ext">bugzilla</literal> hook when they
+	  push changes to the server.  The error message will look
+	  like this:
+	</para>
+	<programlisting>cannot find bugzilla user id for
+	  john.q.public@example.com</programlisting>
+	<para>What this means is that the committer's address,
+	  <literal>john.q.public@example.com</literal>, is not a valid
+	  Bugzilla user name, nor does it have an entry in your
+	  <literal role="rc-usermap">usermap</literal> that maps it to
+	  a valid Bugzilla user name.
+	</para>
+
+      </sect3>
+    </sect2>
+    <sect2>
+      <title><literal role="hg-ext">notify</literal>&emdash;send email
+	notifications</title>
+
+      <para>Although Mercurial's built-in web server provides RSS
+	feeds of changes in every repository, many people prefer to
+	receive change notifications via email.  The <literal
+	  role="hg-ext">notify</literal> hook lets you send out
+	notifications to a set of email addresses whenever changesets
+	arrive that those subscribers are interested in.
+      </para>
+
+      <para>As with the <literal role="hg-ext">bugzilla</literal>
+	hook, the <literal role="hg-ext">notify</literal> hook is
+	template-driven, so you can customise the contents of the
+	notification messages that it sends.
+      </para>
+
+      <para>By default, the <literal role="hg-ext">notify</literal>
+	hook includes a diff of every changeset that it sends out; you
+	can limit the size of the diff, or turn this feature off
+	entirely.  It is useful for letting subscribers review changes
+	immediately, rather than clicking to follow a URL.
+      </para>
+
+      <sect3>
+	<title>Configuring the <literal role="hg-ext">notify</literal>
+	  hook</title>
+
+	<para>You can set up the <literal
+	    role="hg-ext">notify</literal> hook to send one email
+	  message per incoming changeset, or one per incoming group of
+	  changesets (all those that arrived in a single pull or
+	  push).
+	</para>
+	<programlisting>[hooks] # send one email per group of changes
+	  changegroup.notify = python:hgext.notify.hook # send one
+	  email per change incoming.notify =
+	  python:hgext.notify.hook</programlisting>
+
+	<para>Configuration information for this hook lives in the
+	  <literal role="rc-notify">notify</literal> section of a
+	  <filename role="special"> /.hgrc</filename>\ file.
+	</para>
+	<itemizedlist>
+	  <listitem><para><envar role="rc-item-notify">test</envar>:
+	      By default, this hook does not send out email at all;
+	      instead, it prints the message that it
+	      <emphasis>would</emphasis> send.  Set this item to
+	      <literal>false</literal> to allow email to be sent. The
+	      reason that sending of email is turned off by default is
+	      that it takes several tries to configure this extension
+	      exactly as you would like, and it would be bad form to
+	      spam subscribers with a number of <quote>broken</quote>
+	      notifications while you debug your configuration.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-notify">config</envar>:
+	      The path to a configuration file that contains
+	      subscription information.  This is kept separate from
+	      the main <filename role="special"> /.hgrc</filename>\ so
+	      that you can maintain it in a repository of its own.
+	      People can then clone that repository, update their
+	      subscriptions, and push the changes back to your server.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar role="rc-item-notify">strip</envar>:
+	      The number of leading path separator characters to strip
+	      from a repository's path, when deciding whether a
+	      repository has subscribers.  For example, if the
+	      repositories on your server live in <filename
+		class="directory">/home/hg/repos</filename>, and
+	      <literal role="hg-ext">notify</literal> is considering a
+	      repository named <filename
+		class="directory">/home/hg/repos/shared/test</filename>, 
+	      setting <envar role="rc-item-notify">strip</envar> to
+	      <literal>4</literal> will cause <literal
+		role="hg-ext">notify</literal> to trim the path it
+	      considers down to <filename
+		class="directory">shared/test</filename>, and it will
+	      match subscribers against that.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar
+		role="rc-item-notify">template</envar>: The template
+	      text to use when sending messages.  This specifies both
+	      the contents of the message header and its body.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar
+		role="rc-item-notify">maxdiff</envar>: The maximum
+	      number of lines of diff data to append to the end of a
+	      message.  If a diff is longer than this, it is
+	      truncated.  By default, this is set to 300.  Set this to
+	      <literal>0</literal> to omit diffs from notification
+	      emails.
+	    </para>
+	  </listitem>
+	  <listitem><para><envar
+		role="rc-item-notify">sources</envar>: A list of
+	      sources of changesets to consider.  This lets you limit
+	      <literal role="hg-ext">notify</literal> to only sending
+	      out email about changes that remote users pushed into
+	      this repository via a server, for example.  See section
+	      <xref
+		linkend="sec:hook:sources"/> for the sources you can
+	      specify here.
+	    </para>
+	  </listitem></itemizedlist>
+
+	<para>If you set the <envar role="rc-item-web">baseurl</envar>
+	  item in the <literal role="rc-web">web</literal> section,
+	  you can use it in a template; it will be available as
+	  <literal>webroot</literal>.
+	</para>
+
+	<para>Here is an example set of <literal
+	    role="hg-ext">notify</literal> configuration information.
+	</para>
+	<programlisting>
+	  [notify] # really send email test = false # subscriber data
+	  lives in the notify repo config =
+	  /home/hg/repos/notify/notify.conf # repos live in
+	  /home/hg/repos on server, so strip 4 "/" chars strip = 4
+	  template = X-Hg-Repo: {webroot} Subject: {webroot}:
+	  {desc|firstline|strip} From: {author} changeset {node|short}
+	  in {root} details:
+	  {baseurl}{webroot}?cmd=changeset;node={node|short}
+	  description: {desc|tabindent|strip} [web] baseurl =
+	  http://hg.example.com/
+	</programlisting>
+
+	<para>This will produce a message that looks like the
+	  following:
+	</para>
+	<programlisting>
+	  X-Hg-Repo: tests/slave Subject: tests/slave: Handle error
+	  case when slave has no buffers Date: Wed,  2 Aug 2006
+	  15:25:46 -0700 (PDT) changeset 3cba9bfe74b5 in
+	  /home/hg/repos/tests/slave details:
+	  http://hg.example.com/tests/slave?cmd=changeset;node=3cba9bfe74b5 
+	  description: Handle error case when slave has no buffers
+	  diffs (54 lines): diff -r 9d95df7cf2ad -r 3cba9bfe74b5
+	  include/tests.h --- a/include/tests.h      Wed Aug 02
+	  15:19:52 2006 -0700 +++ b/include/tests.h      Wed Aug 02
+	  15:25:26 2006 -0700 @@ -212,6 +212,15 @@ static __inline__
+	  void test_headers(void *h) [...snip...]
+	</programlisting>
+
+      </sect3>
+      <sect3>
+	<title>Testing and troubleshooting</title>
+
+	<para>Do not forget that by default, the <literal
+	    role="hg-ext">notify</literal> extension \emph{will not
+	  send any mail} until you explicitly configure it to do so,
+	  by setting <envar role="rc-item-notify">test</envar> to
+	  <literal>false</literal>.  Until you do that, it simply
+	  prints the message it <emphasis>would</emphasis> send.
+	</para>
+
+      </sect3>
+    </sect2>
+  </sect1>
+  <sect1 id="sec:hook:ref">
+    <title>Information for writers of hooks</title>
+
+    <sect2>
+      <title>In-process hook execution</title>
+
+      <para>An in-process hook is called with arguments of the
+	following form:
+      </para>
+      <programlisting>
+	def myhook(ui, repo, **kwargs): pass
+      </programlisting>
+      <para>The <literal>ui</literal> parameter is a <literal
+	  role="py-mod-mercurial.ui">ui</literal> object. The
+	<literal>repo</literal> parameter is a <literal
+	  role="py-mod-mercurial.localrepo">localrepository</literal>
+	object.  The names and values of the
+	<literal>**kwargs</literal> parameters depend on the hook
+	being invoked, with the following common features:
+      </para>
+      <itemizedlist>
+	<listitem><para>If a parameter is named
+	    <literal>node</literal> or <literal>parentN</literal>, it
+	    will contain a hexadecimal changeset ID. The empty string
+	    is used to represent <quote>null changeset ID</quote>
+	    instead of a string of zeroes.
+	  </para>
+	</listitem>
+	<listitem><para>If a parameter is named
+	    <literal>url</literal>, it will contain the URL of a
+	    remote repository, if that can be determined.
+	  </para>
+	</listitem>
+	<listitem><para>Boolean-valued parameters are represented as
+	    Python <literal>bool</literal> objects.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>An in-process hook is called without a change to the
+	process's working directory (unlike external hooks, which are
+	run in the root of the repository).  It must not change the
+	process's working directory, or it will cause any calls it
+	makes into the Mercurial API to fail.
+      </para>
+
+      <para>If a hook returns a boolean <quote>false</quote> value, it
+	is considered to have succeeded.  If it returns a boolean
+	<quote>true</quote> value or raises an exception, it is
+	considered to have failed.  A useful way to think of the
+	calling convention is <quote>tell me if you fail</quote>.
+      </para>
+
+      <para>Note that changeset IDs are passed into Python hooks as
+	hexadecimal strings, not the binary hashes that Mercurial's
+	APIs normally use.  To convert a hash from hex to binary, use
+	the \pymodfunc{mercurial.node}{bin} function.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>External hook execution</title>
+
+      <para>An external hook is passed to the shell of the user
+	running Mercurial. Features of that shell, such as variable
+	substitution and command redirection, are available.  The hook
+	is run in the root directory of the repository (unlike
+	in-process hooks, which are run in the same directory that
+	Mercurial was run in).
+      </para>
+
+      <para>Hook parameters are passed to the hook as environment
+	variables.  Each environment variable's name is converted in
+	upper case and prefixed with the string
+	<quote><literal>HG_</literal></quote>.  For example, if the
+	name of a parameter is <quote><literal>node</literal></quote>,
+	the name of the environment variable representing that
+	parameter will be <quote><literal>HG_NODE</literal></quote>.
+      </para>
+
+      <para>A boolean parameter is represented as the string
+	<quote><literal>1</literal></quote> for <quote>true</quote>,
+	<quote><literal>0</literal></quote> for <quote>false</quote>.
+	If an environment variable is named <envar>HG_NODE</envar>,
+	<envar>HG_PARENT1</envar> or <envar>HG_PARENT2</envar>, it
+	contains a changeset ID represented as a hexadecimal string.
+	The empty string is used to represent <quote>null changeset
+	  ID</quote> instead of a string of zeroes.  If an environment
+	variable is named <envar>HG_URL</envar>, it will contain the
+	URL of a remote repository, if that can be determined.
+      </para>
+
+      <para>If a hook exits with a status of zero, it is considered to
+	have succeeded.  If it exits with a non-zero status, it is
+	considered to have failed.
+      </para>
+
+    </sect2>
+    <sect2>
+      <title>Finding out where changesets come from</title>
+
+      <para>A hook that involves the transfer of changesets between a
+	local repository and another may be able to find out
+	information about the <quote>far side</quote>.  Mercurial
+	knows <emphasis>how</emphasis> changes are being transferred,
+	and in many cases <emphasis>where</emphasis> they are being
+	transferred to or from.
+      </para>
+
+      <sect3 id="sec:hook:sources">
+	<title>Sources of changesets</title>
+
+	<para>Mercurial will tell a hook what means are, or were, used
+	  to transfer changesets between repositories.  This is
+	  provided by Mercurial in a Python parameter named
+	  <literal>source</literal>, or an environment variable named
+	  <envar>HG_SOURCE</envar>.
+	</para>
+
+	<itemizedlist>
+	  <listitem><para><literal>serve</literal>: Changesets are
+	      transferred to or from a remote repository over http or
+	      ssh.
+	    </para>
+	  </listitem>
+	  <listitem><para><literal>pull</literal>: Changesets are
+	      being transferred via a pull from one repository into
+	      another.
+	    </para>
+	  </listitem>
+	  <listitem><para><literal>push</literal>: Changesets are
+	      being transferred via a push from one repository into
+	      another.
+	    </para>
+	  </listitem>
+	  <listitem><para><literal>bundle</literal>: Changesets are
+	      being transferred to or from a bundle.
+	    </para>
+	  </listitem></itemizedlist>
+
+      </sect3>
+      <sect3 id="sec:hook:url">
+	<title>Where changes are going&emdash;remote repository
+	  URLs</title>
+
+	<para>When possible, Mercurial will tell a hook the location
+	  of the <quote>far side</quote> of an activity that transfers
+	  changeset data between repositories.  This is provided by
+	  Mercurial in a Python parameter named
+	  <literal>url</literal>, or an environment variable named
+	  <envar>HG_URL</envar>.
+	</para>
+
+	<para>This information is not always known.  If a hook is
+	  invoked in a repository that is being served via http or
+	  ssh, Mercurial cannot tell where the remote repository is,
+	  but it may know where the client is connecting from.  In
+	  such cases, the URL will take one of the following forms:
+	</para>
+	<itemizedlist>
+	  <listitem><para><literal>remote:ssh:1.2.3.4</literal>&emdash;remote 
+	      ssh client, at the IP address
+	      <literal>1.2.3.4</literal>.
+	    </para>
+	  </listitem>
+	  <listitem><para><literal>remote:http:1.2.3.4</literal>&emdash;remote 
+	      http client, at the IP address
+	      <literal>1.2.3.4</literal>.  If the client is using SSL,
+	      this will be of the form
+	      <literal>remote:https:1.2.3.4</literal>.
+	    </para>
+	  </listitem>
+	  <listitem><para>Empty&emdash;no information could be
+	      discovered about the remote client.
+	    </para>
+	  </listitem></itemizedlist>
+
+      </sect3>
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Hook reference</title>
+
+    <sect2 id="sec:hook:changegroup">
+      <title><literal role="hook">changegroup</literal>&emdash;after
+	remote changesets added</title>
+
+      <para>This hook is run after a group of pre-existing changesets
+	has been added to the repository, for example via a <command
+	  role="hg-cmd">hg pull</command> or <command role="hg-cmd">hg
+	  unbundle</command>.  This hook is run once per operation
+	that added one or more changesets.  This is in contrast to the
+	<literal role="hook">incoming</literal> hook, which is run
+	once per changeset, regardless of whether the changesets
+	arrive in a group.
+      </para>
+
+      <para>Some possible uses for this hook include kicking off an
+	automated build or test of the added changesets, updating a
+	bug database, or notifying subscribers that a repository
+	contains new changes.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    changeset ID of the first changeset in the group that was
+	    added.  All changesets between this and
+	    \index{tags!<literal>tip</literal>}<literal>tip</literal>,
+	    inclusive, were added by a single <command
+	      role="hg-cmd">hg pull</command>, <command
+	      role="hg-cmd">hg push</command> or <command
+	      role="hg-cmd">hg unbundle</command>.
+	  </para>
+	</listitem>
+	<listitem><para><literal>source</literal>: A string.  The
+	    source of these changes.  See section <xref
+	      linkend="sec:hook:sources"/> for details.
+	  </para>
+	</listitem>
+	<listitem><para><literal>url</literal>: A URL.  The location
+	    of the remote repository, if known.  See section <xref
+	      linkend="sec:hook:url"/> for more
+	    information.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">incoming</literal> (section
+	<xref linkend="sec:hook:incoming"/>), <literal
+	  role="hook">prechangegroup</literal> (section <xref
+	  linkend="sec:hook:prechangegroup"/>), <literal
+	  role="hook">pretxnchangegroup</literal> (section <xref
+	  linkend="sec:hook:pretxnchangegroup"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:commit">
+      <title><literal role="hook">commit</literal>&emdash;after a new
+	changeset is created</title>
+
+      <para>This hook is run after a new changeset has been created.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    changeset ID of the newly committed changeset.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent1</literal>: A changeset ID.
+	    The changeset ID of the first parent of the newly
+	    committed changeset.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent2</literal>: A changeset ID.
+	    The changeset ID of the second parent of the newly
+	    committed changeset.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">precommit</literal>
+	(section <xref linkend="sec:hook:precommit"/>), <literal
+	  role="hook">pretxncommit</literal> (section <xref
+	  linkend="sec:hook:pretxncommit"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:incoming">
+      <title><literal role="hook">incoming</literal>&emdash;after one
+	remote changeset is added</title>
+
+      <para>This hook is run after a pre-existing changeset has been
+	added to the repository, for example via a <command
+	  role="hg-cmd">hg push</command>.  If a group of changesets
+	was added in a single operation, this hook is called once for
+	each added changeset.
+      </para>
+
+      <para>You can use this hook for the same purposes as the
+	<literal role="hook">changegroup</literal> hook (section <xref
+	  linkend="sec:hook:changegroup"/>); it's simply
+	more convenient sometimes to run a hook once per group of
+	changesets, while other times it's handier once per changeset.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    ID of the newly added changeset.
+	  </para>
+	</listitem>
+	<listitem><para><literal>source</literal>: A string.  The
+	    source of these changes.  See section <xref
+	      linkend="sec:hook:sources"/> for details.
+	  </para>
+	</listitem>
+	<listitem><para><literal>url</literal>: A URL.  The location
+	    of the remote repository, if known.  See section <xref
+	      linkend="sec:hook:url"/> for more
+	    information.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">changegroup</literal>
+	(section <xref linkend="sec:hook:changegroup"/>) <literal
+	  role="hook">prechangegroup</literal> (section <xref
+	  linkend="sec:hook:prechangegroup"/>), <literal
+	  role="hook">pretxnchangegroup</literal> (section <xref
+	  linkend="sec:hook:pretxnchangegroup"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:outgoing">
+      <title><literal role="hook">outgoing</literal>&emdash;after
+	changesets are propagated</title>
+
+      <para>This hook is run after a group of changesets has been
+	propagated out of this repository, for example by a <command
+	  role="hg-cmd">hg push</command> or <command role="hg-cmd">hg
+	  bundle</command> command.
+      </para>
+
+      <para>One possible use for this hook is to notify administrators
+	that changes have been pulled.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    changeset ID of the first changeset of the group that was
+	    sent.
+	  </para>
+	</listitem>
+	<listitem><para><literal>source</literal>: A string.  The
+	    source of the of the operation (see section <xref
+	      linkend="sec:hook:sources"/>).  If a remote
+	    client pulled changes from this repository,
+	    <literal>source</literal> will be
+	    <literal>serve</literal>.  If the client that obtained
+	    changes from this repository was local,
+	    <literal>source</literal> will be
+	    <literal>bundle</literal>, <literal>pull</literal>, or
+	    <literal>push</literal>, depending on the operation the
+	    client performed.
+	  </para>
+	</listitem>
+	<listitem><para><literal>url</literal>: A URL.  The location
+	    of the remote repository, if known.  See section <xref
+	      linkend="sec:hook:url"/> for more
+	    information.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">preoutgoing</literal>
+	(section <xref linkend="sec:hook:preoutgoing"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:prechangegroup">
+      <title><literal
+	  role="hook">prechangegroup</literal>&emdash;before starting
+	to add remote changesets</title>
+
+      <para>This controlling hook is run before Mercurial begins to
+	add a group of changesets from another repository.
+      </para>
+
+      <para>This hook does not have any information about the
+	changesets to be added, because it is run before transmission
+	of those changesets is allowed to begin.  If this hook fails,
+	the changesets will not be transmitted.
+      </para>
+
+      <para>One use for this hook is to prevent external changes from
+	being added to a repository.  For example, you could use this
+	to <quote>freeze</quote> a server-hosted branch temporarily or
+	permanently so that users cannot push to it, while still
+	allowing a local administrator to modify the repository.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>source</literal>: A string.  The
+	    source of these changes.  See section <xref
+	      linkend="sec:hook:sources"/> for details.
+	  </para>
+	</listitem>
+	<listitem><para><literal>url</literal>: A URL.  The location
+	    of the remote repository, if known.  See section <xref
+	      linkend="sec:hook:url"/> for more
+	    information.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">changegroup</literal>
+	(section <xref linkend="sec:hook:changegroup"/>), <literal
+	  role="hook">incoming</literal> (section <xref
+	  linkend="sec:hook:incoming"/>), , <literal
+	  role="hook">pretxnchangegroup</literal> (section <xref
+	  linkend="sec:hook:pretxnchangegroup"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:precommit">
+      <title><literal role="hook">precommit</literal>&emdash;before
+	starting to commit a changeset</title>
+
+      <para>This hook is run before Mercurial begins to commit a new
+	changeset. It is run before Mercurial has any of the metadata
+	for the commit, such as the files to be committed, the commit
+	message, or the commit date.
+      </para>
+
+      <para>One use for this hook is to disable the ability to commit
+	new changesets, while still allowing incoming changesets.
+	Another is to run a build or test, and only allow the commit
+	to begin if the build or test succeeds.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>parent1</literal>: A changeset ID.
+	    The changeset ID of the first parent of the working
+	    directory.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent2</literal>: A changeset ID.
+	    The changeset ID of the second parent of the working
+	    directory.
+	  </para>
+	</listitem></itemizedlist>
+      <para>If the commit proceeds, the parents of the working
+	directory will become the parents of the new changeset.
+      </para>
+
+      <para>See also: <literal role="hook">commit</literal> (section
+	<xref linkend="sec:hook:commit"/>), <literal
+	  role="hook">pretxncommit</literal> (section <xref
+	  linkend="sec:hook:pretxncommit"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:preoutgoing">
+      <title><literal role="hook">preoutgoing</literal>&emdash;before
+	starting to propagate changesets</title>
+
+      <para>This hook is invoked before Mercurial knows the identities
+	of the changesets to be transmitted.
+      </para>
+
+      <para>One use for this hook is to prevent changes from being
+	transmitted to another repository.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>source</literal>: A string.  The
+	    source of the operation that is attempting to obtain
+	    changes from this repository (see section <xref
+	      linkend="sec:hook:sources"/>).  See the documentation
+	    for the <literal>source</literal> parameter to the
+	    <literal role="hook">outgoing</literal> hook, in section
+	    <xref linkend="sec:hook:outgoing"/>, for possible values
+	    of
+	    this parameter.
+	  </para>
+	</listitem>
+	<listitem><para><literal>url</literal>: A URL.  The location
+	    of the remote repository, if known.  See section <xref
+	      linkend="sec:hook:url"/> for more
+	    information.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">outgoing</literal> (section
+	<xref linkend="sec:hook:outgoing"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:pretag">
+      <title><literal role="hook">pretag</literal>&emdash;before
+	tagging a changeset</title>
+
+      <para>This controlling hook is run before a tag is created.  If
+	the hook succeeds, creation of the tag proceeds.  If the hook
+	fails, the tag is not created.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>local</literal>: A boolean.  Whether
+	    the tag is local to this repository instance (i.e. stored
+	    in <filename role="special">.hg/localtags</filename>) or
+	    managed by Mercurial (stored in <filename
+	      role="special">.hgtags</filename>).
+	  </para>
+	</listitem>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    ID of the changeset to be tagged.
+	  </para>
+	</listitem>
+	<listitem><para><literal>tag</literal>: A string.  The name of
+	    the tag to be created.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>If the tag to be created is revision-controlled, the
+	<literal role="hook">precommit</literal> and <literal
+	  role="hook">pretxncommit</literal> hooks (sections <xref
+	  linkend="sec:hook:commit"/> and <xref
+	  linkend="sec:hook:pretxncommit"/>) will also be run.
+      </para>
+
+      <para>See also: <literal role="hook">tag</literal> (section
+	<xref linkend="sec:hook:tag"/>)
+      </para>
+    </sect2>
+    <sect2 id="sec:hook:pretxnchangegroup">
+      <title><literal
+	  role="hook">pretxnchangegroup</literal>&emdash;before
+	completing addition of remote changesets</title>
+
+      <para>This controlling hook is run before a
+	transaction&emdash;that manages the addition of a group of new
+	changesets from outside the repository&emdash;completes.  If
+	the hook succeeds, the transaction completes, and all of the
+	changesets become permanent within this repository.  If the
+	hook fails, the transaction is rolled back, and the data for
+	the changesets is erased.
+      </para>
+
+      <para>This hook can access the metadata associated with the
+	almost-added changesets, but it should not do anything
+	permanent with this data. It must also not modify the working
+	directory.
+      </para>
+
+      <para>While this hook is running, if other Mercurial processes
+	access this repository, they will be able to see the
+	almost-added changesets as if they are permanent.  This may
+	lead to race conditions if you do not take steps to avoid
+	them.
+      </para>
+
+      <para>This hook can be used to automatically vet a group of
+	changesets.  If the hook fails, all of the changesets are
+	<quote>rejected</quote> when the transaction rolls back.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    changeset ID of the first changeset in the group that was
+	    added.  All changesets between this and
+	    \index{tags!<literal>tip</literal>}<literal>tip</literal>,
+	    inclusive, were added by a single <command
+	      role="hg-cmd">hg pull</command>, <command
+	      role="hg-cmd">hg push</command> or <command
+	      role="hg-cmd">hg unbundle</command>.
+	  </para>
+	</listitem>
+	<listitem><para><literal>source</literal>: A string.  The
+	    source of these changes.  See section <xref
+	      linkend="sec:hook:sources"/> for details.
+	  </para>
+	</listitem>
+	<listitem><para><literal>url</literal>: A URL.  The location
+	    of the remote repository, if known.  See section <xref
+	      linkend="sec:hook:url"/> for more
+	    information.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">changegroup</literal>
+	(section <xref linkend="sec:hook:changegroup"/>), <literal
+	  role="hook">incoming</literal> (section <xref
+	  linkend="sec:hook:incoming"/>), <literal
+	  role="hook">prechangegroup</literal> (section <xref
+	  linkend="sec:hook:prechangegroup"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:pretxncommit">
+      <title><literal role="hook">pretxncommit</literal>&emdash;before
+	completing commit of new changeset</title>
+
+      <para>This controlling hook is run before a
+	transaction&emdash;that manages a new commit&emdash;completes.
+	If the hook succeeds, the transaction completes and the
+	changeset becomes permanent within this repository.  If the
+	hook fails, the transaction is rolled back, and the commit
+	data is erased.
+      </para>
+
+      <para>This hook can access the metadata associated with the
+	almost-new changeset, but it should not do anything permanent
+	with this data.  It must also not modify the working
+	directory.
+      </para>
+
+      <para>While this hook is running, if other Mercurial processes
+	access this repository, they will be able to see the
+	almost-new changeset as if it is permanent.  This may lead to
+	race conditions if you do not take steps to avoid them.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    changeset ID of the newly committed changeset.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent1</literal>: A changeset ID.
+	    The changeset ID of the first parent of the newly
+	    committed changeset.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent2</literal>: A changeset ID.
+	    The changeset ID of the second parent of the newly
+	    committed changeset.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">precommit</literal>
+	(section <xref linkend="sec:hook:precommit"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:preupdate">
+      <title><literal role="hook">preupdate</literal>&emdash;before
+	updating or merging working directory</title>
+
+      <para>This controlling hook is run before an update or merge of
+	the working directory begins.  It is run only if Mercurial's
+	normal pre-update checks determine that the update or merge
+	can proceed.  If the hook succeeds, the update or merge may
+	proceed; if it fails, the update or merge does not start.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>parent1</literal>: A changeset ID.
+	    The ID of the parent that the working directory is to be
+	    updated to.  If the working directory is being merged, it
+	    will not change this parent.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent2</literal>: A changeset ID.
+	    Only set if the working directory is being merged.  The ID
+	    of the revision that the working directory is being merged
+	    with.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">update</literal> (section
+	<xref linkend="sec:hook:update"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:tag">
+      <title><literal role="hook">tag</literal>&emdash;after tagging a
+	changeset</title>
+
+      <para>This hook is run after a tag has been created.
+      </para>
+
+      <para>Parameters to this hook:
+      </para>
+      <itemizedlist>
+	<listitem><para><literal>local</literal>: A boolean.  Whether
+	    the new tag is local to this repository instance (i.e.
+	    stored in <filename
+	      role="special">.hg/localtags</filename>) or managed by
+	    Mercurial (stored in <filename
+	      role="special">.hgtags</filename>).
+	  </para>
+	</listitem>
+	<listitem><para><literal>node</literal>: A changeset ID.  The
+	    ID of the changeset that was tagged.
+	  </para>
+	</listitem>
+	<listitem><para><literal>tag</literal>: A string.  The name of
+	    the tag that was created.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>If the created tag is revision-controlled, the <literal
+	  role="hook">commit</literal> hook (section <xref
+	  linkend="sec:hook:commit"/>) is run before this hook.
+      </para>
+
+      <para>See also: <literal role="hook">pretag</literal> (section
+	<xref linkend="sec:hook:pretag"/>)
+      </para>
+
+    </sect2>
+    <sect2 id="sec:hook:update">
+      <title><literal role="hook">update</literal>&emdash;after
+	updating or merging working directory</title>
+
+      <para>This hook is run after an update or merge of the working
+	directory completes.  Since a merge can fail (if the external
+	<command>hgmerge</command> command fails to resolve conflicts
+	in a file), this hook communicates whether the update or merge
+	completed cleanly.
+      </para>
+
+      <itemizedlist>
+	<listitem><para><literal>error</literal>: A boolean.
+	    Indicates whether the update or merge completed
+	    successfully.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent1</literal>: A changeset ID.
+	    The ID of the parent that the working directory was
+	    updated to.  If the working directory was merged, it will
+	    not have changed this parent.
+	  </para>
+	</listitem>
+	<listitem><para><literal>parent2</literal>: A changeset ID.
+	    Only set if the working directory was merged.  The ID of
+	    the revision that the working directory was merged with.
+	  </para>
+	</listitem></itemizedlist>
+
+      <para>See also: <literal role="hook">preupdate</literal>
+	(section <xref linkend="sec:hook:preupdate"/>)
+      </para>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch11-template.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch11-template.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,673 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:template">
+  <title>Customising the output of Mercurial</title>
+
+  <para>Mercurial provides a powerful mechanism to let you control how
+    it displays information.  The mechanism is based on templates.
+    You can use templates to generate specific output for a single
+    command, or to customise the entire appearance of the built-in web
+    interface.</para>
+
+  <sect1 id="sec:style">
+    <title>Using precanned output styles</title>
+
+    <para>Packaged with Mercurial are some output styles that you can
+      use immediately.  A style is simply a precanned template that
+      someone wrote and installed somewhere that Mercurial can
+      find.</para>
+
+    <para>Before we take a look at Mercurial's bundled styles, let's
+      review its normal output.</para>
+
+    <para><!-- &interaction.template.simple.normal; --></para>
+
+    <para>This is somewhat informative, but it takes up a lot of
+      space&emdash;five lines of output per changeset.  The
+      <literal>compact</literal> style reduces this to three lines,
+      presented in a sparse manner.</para>
+
+    <para><!-- &interaction.template.simple.compact; --></para>
+
+    <para>The <literal>changelog</literal> style hints at the
+      expressive power of Mercurial's templating engine.  This style
+      attempts to follow the GNU Project's changelog
+      guidelines<citation>web:changelog</citation>.</para>
+
+    <para><!-- &interaction.template.simple.changelog; --></para>
+
+    <para>You will not be shocked to learn that Mercurial's default
+      output style is named <literal>default</literal>.</para>
+
+    <sect2>
+      <title>Setting a default style</title>
+
+      <para>You can modify the output style that Mercurial will use
+	for every command by editing your <filename role="special">
+	  /.hgrc</filename>\ file, naming the style you would prefer
+	to use.</para>
+
+      <programlisting>[ui] style = compact</programlisting>
+
+      <para>If you write a style of your own, you can use it by either
+	providing the path to your style file, or copying your style
+	file into a location where Mercurial can find it (typically
+	the <literal>templates</literal> subdirectory of your
+	Mercurial install directory).</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Commands that support styles and templates</title>
+
+    <para>All of Mercurial's
+      <quote><literal>log</literal>-like</quote> commands let you use
+      styles and templates: <command role="hg-cmd">hg
+	incoming</command>, <command role="hg-cmd">hg log</command>,
+      <command role="hg-cmd">hg outgoing</command>, and <command
+	role="hg-cmd">hg tip</command>.</para>
+
+    <para>As I write this manual, these are so far the only commands
+      that support styles and templates.  Since these are the most
+      important commands that need customisable output, there has been
+      little pressure from the Mercurial user community to add style
+      and template support to other commands.</para>
+
+  </sect1>
+  <sect1>
+    <title>The basics of templating</title>
+
+    <para>At its simplest, a Mercurial template is a piece of text.
+      Some of the text never changes, while other parts are
+      <emphasis>expanded</emphasis>, or replaced with new text, when
+      necessary.</para>
+
+    <para>Before we continue, let's look again at a simple example of
+      Mercurial's normal output.</para>
+
+    <para><!-- &interaction.template.simple.normal; --></para>
+
+    <para>Now, let's run the same command, but using a template to
+      change its output.</para>
+
+    <para><!-- &interaction.template.simple.simplest; --></para>
+
+    <para>The example above illustrates the simplest possible
+      template; it's just a piece of static text, printed once for
+      each changeset.  The <option
+	role="hg-opt-log">--template</option> option to the <command
+	role="hg-cmd">hg log</command> command tells Mercurial to use
+      the given text as the template when printing each
+      changeset.</para>
+
+    <para>Notice that the template string above ends with the text
+      <quote><literal>\n</literal></quote>.  This is an
+      <emphasis>escape sequence</emphasis>, telling Mercurial to print
+      a newline at the end of each template item.  If you omit this
+      newline, Mercurial will run each piece of output together.  See
+      section <xref linkend="sec:template:escape"/> for more details
+      of escape sequences.</para>
+
+    <para>A template that prints a fixed string of text all the time
+      isn't very useful; let's try something a bit more
+      complex.</para>
+
+    <para><!-- &interaction.template.simple.simplesub; --></para>
+
+    <para>As you can see, the string
+      <quote><literal>{desc}</literal></quote> in the template has
+      been replaced in the output with the description of each
+      changeset.  Every time Mercurial finds text enclosed in curly
+      braces (<quote><literal>{</literal></quote> and
+      <quote>\texttt{}}</quote>), it will try to replace the braces
+      and text with the expansion of whatever is inside.  To print a
+      literal curly brace, you must escape it, as described in section
+      <xref
+	linkend="sec:template:escape"/>.</para>
+
+  </sect1>
+  <sect1 id="sec:template:keyword">
+    <title>Common template keywords</title>
+
+    <para>You can start writing simple templates immediately using the
+      keywords below.</para>
+
+    <itemizedlist>
+      <listitem><para><literal
+	    role="template-keyword">author</literal>: String.  The
+	  unmodified author of the changeset.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-keyword">branches</literal>: String.  The
+	  name of the branch on which the changeset was committed.
+	  Will be empty if the branch name was
+	  <literal>default</literal>.</para>
+      </listitem>
+      <listitem><para><literal role="template-keyword">date</literal>:
+	  Date information.  The date when the changeset was
+	  committed.  This is <emphasis>not</emphasis> human-readable;
+	  you must pass it through a filter that will render it
+	  appropriately.  See section <xref
+	    linkend="sec:template:filter"/> for more information
+	  on filters. The date is expressed as a pair of numbers.  The
+	  first number is a Unix UTC timestamp (seconds since January
+	  1, 1970); the second is the offset of the committer's
+	  timezone from UTC, in seconds.</para>
+      </listitem>
+      <listitem><para><literal role="template-keyword">desc</literal>:
+	  String.  The text of the changeset description.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-keyword">files</literal>: List of strings.
+	  All files modified, added, or removed by this
+	  changeset.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-keyword">file_adds</literal>: List of
+	  strings.  Files added by this changeset.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-keyword">file_dels</literal>: List of
+	  strings.  Files removed by this changeset.</para>
+      </listitem>
+      <listitem><para><literal role="template-keyword">node</literal>:
+	  String.  The changeset identification hash, as a
+	  40-character hexadecimal string.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-keyword">parents</literal>: List of
+	  strings.  The parents of the changeset.</para>
+      </listitem>
+      <listitem><para><literal role="template-keyword">rev</literal>:
+	  Integer.  The repository-local changeset revision
+	  number.</para>
+      </listitem>
+      <listitem><para><literal role="template-keyword">tags</literal>:
+	  List of strings.  Any tags associated with the
+	  changeset.</para>
+      </listitem></itemizedlist>
+
+    <para>A few simple experiments will show us what to expect when we
+      use these keywords; you can see the results below.</para>
+
+<!-- &interaction.template.simple.keywords; -->
+
+    <para>As we noted above, the date keyword does not produce
+      human-readable output, so we must treat it specially.  This
+      involves using a <emphasis>filter</emphasis>, about which more
+      in section <xref
+	linkend="sec:template:filter"/>.</para>
+
+    <para><!-- &interaction.template.simple.datekeyword; --></para>
+
+  </sect1>
+  <sect1 id="sec:template:escape">
+    <title>Escape sequences</title>
+
+    <para>Mercurial's templating engine recognises the most commonly
+      used escape sequences in strings.  When it sees a backslash
+      (<quote><literal>\</literal></quote>) character, it looks at the
+      following character and substitutes the two characters with a
+      single replacement, as described below.</para>
+
+    <itemizedlist>
+      <listitem><para><literal>\textbackslash\textbackslash</literal>:
+	  Backslash, <quote><literal>\</literal></quote>, ASCII
+	  134.</para>
+      </listitem>
+      <listitem><para><literal>\textbackslash n</literal>: Newline,
+	  ASCII 12.</para>
+      </listitem>
+      <listitem><para><literal>\textbackslash r</literal>: Carriage
+	  return, ASCII 15.</para>
+      </listitem>
+      <listitem><para><literal>\textbackslash t</literal>: Tab, ASCII
+	  11.</para>
+      </listitem>
+      <listitem><para><literal>\textbackslash v</literal>: Vertical
+	  tab, ASCII 13.</para>
+      </listitem>
+      <listitem><para><literal>\textbackslash {</literal>: Open curly
+	  brace, <quote><literal>{</literal></quote>, ASCII
+	  173.</para>
+      </listitem>
+      <listitem><para><literal>\textbackslash }</literal>: Close curly
+	  brace, <quote><literal>}</literal></quote>, ASCII
+	  175.</para>
+      </listitem></itemizedlist>
+
+    <para>As indicated above, if you want the expansion of a template
+      to contain a literal <quote><literal>\</literal></quote>,
+      <quote><literal>{</literal></quote>, or
+      <quote><literal>{</literal></quote> character, you must escape
+      it.</para>
+
+  </sect1>
+  <sect1 id="sec:template:filter">
+    <title>Filtering keywords to change their results</title>
+
+    <para>Some of the results of template expansion are not
+      immediately easy to use.  Mercurial lets you specify an optional
+      chain of <emphasis>filters</emphasis> to modify the result of
+      expanding a keyword.  You have already seen a common filter,
+      <literal role="template-kw-filt-date">isodate</literal>, in
+      action above, to make a date readable.</para>
+
+    <para>Below is a list of the most commonly used filters that
+      Mercurial supports.  While some filters can be applied to any
+      text, others can only be used in specific circumstances.  The
+      name of each filter is followed first by an indication of where
+      it can be used, then a description of its effect.</para>
+
+    <itemizedlist>
+      <listitem><para><literal
+	    role="template-filter">addbreaks</literal>: Any text. Add
+	  an XHTML <quote><literal>&lt;br/&gt;</literal></quote> tag
+	  before the end of every line except the last.  For example,
+	  <quote><literal>foo\nbar</literal></quote> becomes
+	  <quote><literal>foo&lt;br/&gt;\nbar</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-date">age</literal>: <literal
+	    role="template-keyword">date</literal> keyword.  Render
+	  the age of the date, relative to the current time.  Yields a
+	  string like <quote><literal>10
+	      minutes</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">basename</literal>: Any text, but
+	  most useful for the <literal
+	    role="template-keyword">files</literal> keyword and its
+	  relatives.  Treat the text as a path, and return the
+	  basename. For example,
+	  <quote><literal>foo/bar/baz</literal></quote> becomes
+	  <quote><literal>baz</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-date">date</literal>: <literal
+	    role="template-keyword">date</literal> keyword.  Render a
+	  date in a similar format to the Unix <literal
+	    role="template-keyword">date</literal> command, but with
+	  timezone included.  Yields a string like <quote><literal>Mon
+	      Sep 04 15:13:13 2006 -0700</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-author">domain</literal>: Any text,
+	  but most useful for the <literal
+	    role="template-keyword">author</literal> keyword.  Finds
+	  the first string that looks like an email address, and
+	  extract just the domain component.  For example,
+	  <quote><literal>Bryan O'Sullivan
+	      &lt;bos@serpentine.com&gt;</literal></quote> becomes
+	  <quote><literal>serpentine.com</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-author">email</literal>: Any text,
+	  but most useful for the <literal
+	    role="template-keyword">author</literal> keyword.  Extract
+	  the first string that looks like an email address.  For
+	  example, <quote><literal>Bryan O'Sullivan
+	      &lt;bos@serpentine.com&gt;</literal></quote> becomes
+	  <quote><literal>bos@serpentine.com</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">escape</literal>: Any text.
+	  Replace the special XML/XHTML characters
+	  <quote><literal>&amp;</literal></quote>,
+	  <quote><literal>&lt;</literal></quote> and
+	  <quote><literal>&gt;</literal></quote> with XML
+	  entities.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">fill68</literal>: Any text.  Wrap
+	  the text to fit in 68 columns.  This is useful before you
+	  pass text through the <literal
+	    role="template-filter">tabindent</literal> filter, and
+	  still want it to fit in an 80-column fixed-font
+	  window.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">fill76</literal>: Any text.  Wrap
+	  the text to fit in 76 columns.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">firstline</literal>: Any text.
+	  Yield the first line of text, without any trailing
+	  newlines.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-date">hgdate</literal>: <literal
+	    role="template-keyword">date</literal> keyword.  Render
+	  the date as a pair of readable numbers.  Yields a string
+	  like <quote><literal>1157407993
+	      25200</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-date">isodate</literal>: <literal
+	    role="template-keyword">date</literal> keyword.  Render
+	  the date as a text string in ISO 8601 format.  Yields a
+	  string like <quote><literal>2006-09-04 15:13:13
+	      -0700</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">obfuscate</literal>: Any text, but
+	  most useful for the <literal
+	    role="template-keyword">author</literal> keyword.  Yield
+	  the input text rendered as a sequence of XML entities.  This
+	  helps to defeat some particularly stupid screen-scraping
+	  email harvesting spambots.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-author">person</literal>: Any text,
+	  but most useful for the <literal
+	    role="template-keyword">author</literal> keyword.  Yield
+	  the text before an email address. For example,
+	  <quote><literal>Bryan O'Sullivan
+	      &lt;bos@serpentine.com&gt;</literal></quote> becomes
+	  <quote><literal>Bryan O'Sullivan</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-date">rfc822date</literal>:
+	  <literal role="template-keyword">date</literal> keyword.
+	  Render a date using the same format used in email headers.
+	  Yields a string like <quote><literal>Mon, 04 Sep 2006
+	      15:13:13 -0700</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-node">short</literal>: Changeset
+	  hash.  Yield the short form of a changeset hash, i.e. a
+	  12-character hexadecimal string.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-date">shortdate</literal>: <literal
+	    role="template-keyword">date</literal> keyword.  Render
+	  the year, month, and day of the date.  Yields a string like
+	  <quote><literal>2006-09-04</literal></quote>.</para>
+      </listitem>
+      <listitem><para><literal role="template-filter">strip</literal>:
+	  Any text.  Strip all leading and trailing whitespace from
+	  the string.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">tabindent</literal>: Any text.
+	  Yield the text, with every line except the first starting
+	  with a tab character.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-filter">urlescape</literal>: Any text.
+	  Escape all characters that are considered
+	  <quote>special</quote> by URL parsers.  For example,
+	  <literal>foo bar</literal> becomes
+	  <literal>foo%20bar</literal>.</para>
+      </listitem>
+      <listitem><para><literal
+	    role="template-kw-filt-author">user</literal>: Any text,
+	  but most useful for the <literal
+	    role="template-keyword">author</literal> keyword.  Return
+	  the <quote>user</quote> portion of an email address.  For
+	  example, <quote><literal>Bryan O'Sullivan
+	      &lt;bos@serpentine.com&gt;</literal></quote> becomes
+	  <quote><literal>bos</literal></quote>.</para>
+      </listitem></itemizedlist>
+
+<!-- &interaction.template.simple.manyfilters; -->
+
+    <note>
+      <para>  If you try to apply a filter to a piece of data that it
+	cannot process, Mercurial will fail and print a Python
+	exception.  For example, trying to run the output of the
+	<literal role="template-keyword">desc</literal> keyword into
+	the <literal role="template-kw-filt-date">isodate</literal>
+	filter is not a good idea.</para>
+    </note>
+
+    <sect2>
+      <title>Combining filters</title>
+
+      <para>It is easy to combine filters to yield output in the form
+	you would like.  The following chain of filters tidies up a
+	description, then makes sure that it fits cleanly into 68
+	columns, then indents it by a further 8 characters (at least
+	on Unix-like systems, where a tab is conventionally 8
+	characters wide).</para>
+
+      <para><!-- &interaction.template.simple.combine; --></para>
+
+      <para>Note the use of <quote><literal>\t</literal></quote> (a
+	tab character) in the template to force the first line to be
+	indented; this is necessary since <literal
+	  role="template-keyword">tabindent</literal> indents all
+	lines <emphasis>except</emphasis> the first.</para>
+
+      <para>Keep in mind that the order of filters in a chain is
+	significant.  The first filter is applied to the result of the
+	keyword; the second to the result of the first filter; and so
+	on.  For example, using <literal>fill68|tabindent</literal>
+	gives very different results from
+	<literal>tabindent|fill68</literal>.</para>
+
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>From templates to styles</title>
+
+    <para>A command line template provides a quick and simple way to
+      format some output.  Templates can become verbose, though, and
+      it's useful to be able to give a template a name.  A style file
+      is a template with a name, stored in a file.</para>
+
+    <para>More than that, using a style file unlocks the power of
+      Mercurial's templating engine in ways that are not possible
+      using the command line <option
+	role="hg-opt-log">--template</option> option.</para>
+
+    <sect2>
+      <title>The simplest of style files</title>
+
+      <para>Our simple style file contains just one line:</para>
+
+      <para><!-- &interaction.template.simple.rev; --></para>
+
+      <para>This tells Mercurial, <quote>if you're printing a
+	  changeset, use the text on the right as the
+	  template</quote>.</para>
+
+    </sect2>
+    <sect2>
+      <title>Style file syntax</title>
+
+      <para>The syntax rules for a style file are simple.</para>
+
+      <itemizedlist>
+	<listitem><para>The file is processed one line at a
+	    time.</para>
+	</listitem>
+	<listitem><para>Leading and trailing white space are
+	    ignored.</para>
+	</listitem>
+	<listitem><para>Empty lines are skipped.</para>
+	</listitem>
+	<listitem><para>If a line starts with either of the characters
+	    <quote><literal>#</literal></quote> or
+	    <quote><literal>;</literal></quote>, the entire line is
+	    treated as a comment, and skipped as if empty.</para>
+	</listitem>
+	<listitem><para>A line starts with a keyword.  This must start
+	    with an alphabetic character or underscore, and can
+	    subsequently contain any alphanumeric character or
+	    underscore.  (In regexp notation, a keyword must match
+	    <literal>[A-Za-z_][A-Za-z0-9_]*</literal>.)</para>
+	</listitem>
+	<listitem><para>The next element must be an
+	    <quote><literal>=</literal></quote> character, which can
+	    be preceded or followed by an arbitrary amount of white
+	    space.</para>
+	</listitem>
+	<listitem><para>If the rest of the line starts and ends with
+	    matching quote characters (either single or double quote),
+	    it is treated as a template body.</para>
+	</listitem>
+	<listitem><para>If the rest of the line <emphasis>does
+	      not</emphasis> start with a quote character, it is
+	    treated as the name of a file; the contents of this file
+	    will be read and used as a template body.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Style files by example</title>
+
+    <para>To illustrate how to write a style file, we will construct a
+      few by example.  Rather than provide a complete style file and
+      walk through it, we'll mirror the usual process of developing a
+      style file by starting with something very simple, and walking
+      through a series of successively more complete examples.</para>
+
+    <sect2>
+      <title>Identifying mistakes in style files</title>
+
+      <para>If Mercurial encounters a problem in a style file you are
+	working on, it prints a terse error message that, once you
+	figure out what it means, is actually quite useful.</para>
+
+<!-- &interaction.template.svnstyle.syntax.input; -->
+
+      <para>Notice that <filename>broken.style</filename> attempts to
+	define a <literal>changeset</literal> keyword, but forgets to
+	give any content for it. When instructed to use this style
+	file, Mercurial promptly complains.</para>
+
+      <para><!-- &interaction.template.svnstyle.syntax.error;
+	--></para>
+
+      <para>This error message looks intimidating, but it is not too
+	hard to follow.</para>
+
+      <itemizedlist>
+	<listitem><para>The first component is simply Mercurial's way
+	    of saying <quote>I am giving up</quote>.</para>
+	  <programlisting>___abort___: broken.style:1: parse
+	    error</programlisting>
+	</listitem>
+	<listitem><para>Next comes the name of the style file that
+	    contains the error.</para>
+	  <programlisting>
+	    abort: ___broken.style___:1: parse error
+	  </programlisting>
+	</listitem>
+	<listitem><para>Following the file name is the line number
+	    where the error was encountered.</para>
+	  <programlisting>abort: broken.style:___1___: parse
+	    error</programlisting>
+	</listitem>
+	<listitem><para>Finally, a description of what went
+	    wrong.</para>
+	  <programlisting>abort: broken.style:1: ___parse
+	    error___</programlisting>
+	</listitem>
+	<listitem><para>The description of the problem is not always
+	    clear (as in this case), but even when it is cryptic, it
+	    is almost always trivial to visually inspect the offending
+	    line in the style file and see what is wrong.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title>Uniquely identifying a repository</title>
+
+      <para>If you would like to be able to identify a Mercurial
+	repository <quote>fairly uniquely</quote> using a short string
+	as an identifier, you can use the first revision in the
+	repository. <!-- &interaction.template.svnstyle.id; --> This
+	is not guaranteed to be unique, but it is nevertheless useful
+	in many cases.</para>
+      <itemizedlist>
+	<listitem><para>It will not work in a completely empty
+	    repository, because such a repository does not have a
+	    revision zero.</para>
+	</listitem>
+	<listitem><para>Neither will it work in the (extremely rare)
+	    case where a repository is a merge of two or more formerly
+	    independent repositories, and you still have those
+	    repositories around.</para>
+	</listitem></itemizedlist>
+      <para>Here are some uses to which you could put this
+	identifier:</para>
+      <itemizedlist>
+	<listitem><para>As a key into a table for a database that
+	    manages repositories on a server.</para>
+	</listitem>
+	<listitem><para>As half of a {<emphasis>repository
+	      ID</emphasis>, <emphasis>revision ID</emphasis>} tuple.
+	    Save this information away when you run an automated build
+	    or other activity, so that you can <quote>replay</quote>
+	    the build later if necessary.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+    <sect2>
+      <title>Mimicking Subversion's output</title>
+
+      <para>Let's try to emulate the default output format used by
+	another revision control tool, Subversion. <!--
+	&interaction.template.svnstyle.short; --></para>
+
+      <para>Since Subversion's output style is fairly simple, it is
+	easy to copy-and-paste a hunk of its output into a file, and
+	replace the text produced above by Subversion with the
+	template values we'd like to see expanded. <!--
+	&interaction.template.svnstyle.template; --></para>
+
+      <para>There are a few small ways in which this template deviates
+	from the output produced by Subversion.</para>
+      <itemizedlist>
+	<listitem><para>Subversion prints a <quote>readable</quote>
+	    date (the <quote>\texttt{Wed, 27 Sep 2006}</quote> in the
+	    example output above) in parentheses.  Mercurial's
+	    templating engine does not provide a way to display a date
+	    in this format without also printing the time and time
+	    zone.</para>
+	</listitem>
+	<listitem><para>We emulate Subversion's printing of
+	    <quote>separator</quote> lines full of
+	    <quote><literal>-</literal></quote> characters by ending
+	    the template with such a line. We use the templating
+	    engine's <literal role="template-keyword">header</literal>
+	    keyword to print a separator line as the first line of
+	    output (see below), thus achieving similar output to
+	    Subversion.</para>
+	</listitem>
+	<listitem><para>Subversion's output includes a count in the
+	    header of the number of lines in the commit message.  We
+	    cannot replicate this in Mercurial; the templating engine
+	    does not currently provide a filter that counts the number
+	    of lines the template generates.</para>
+	</listitem></itemizedlist>
+      <para>It took me no more than a minute or two of work to replace
+	literal text from an example of Subversion's output with some
+	keywords and filters to give the template above.  The style
+	file simply refers to the template. <!--
+	&interaction.template.svnstyle.style; --></para>
+
+      <para>We could have included the text of the template file
+	directly in the style file by enclosing it in quotes and
+	replacing the newlines with
+	<quote><literal>\n</literal></quote> sequences, but it would
+	have made the style file too difficult to read.  Readability
+	is a good guide when you're trying to decide whether some text
+	belongs in a style file, or in a template file that the style
+	file points to.  If the style file will look too big or
+	cluttered if you insert a literal piece of text, drop it into
+	a template instead.</para>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch12-mq.xml
--- a/en/ch12-mq.xml	Mon Feb 09 23:25:40 2009 -0800
+++ b/en/ch12-mq.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -36,17 +36,17 @@
     <para>When you have few changes to maintain, it is easy to manage
       a single patch using the standard <command>diff</command> and
       <command>patch</command> programs (see section <xref
-	linkend="sec:mq:patch"/> for a discussion of these tools).
-      Once the number of changes grows, it starts to make sense to
-      maintain patches as discrete <quote>chunks of work,</quote> so
-      that for example a single patch will contain only one bug fix
-      (the patch might modify several files, but it's doing
-      <quote>only one thing</quote>), and you may have a number of
-      such patches for different bugs you need fixed and local changes
-      you require.  In this situation, if you submit a bug fix patch
-      to the upstream maintainers of a package and they include your
-      fix in a subsequent release, you can simply drop that single
-      patch when you're updating to the newer release.</para>
+	linkend="sec:mq:patch"/> for a discussion of these
+      tools). Once the number of changes grows, it starts to make
+      sense to maintain patches as discrete <quote>chunks of
+	work,</quote> so that for example a single patch will contain
+      only one bug fix (the patch might modify several files, but it's
+      doing <quote>only one thing</quote>), and you may have a number
+      of such patches for different bugs you need fixed and local
+      changes you require.  In this situation, if you submit a bug fix
+      patch to the upstream maintainers of a package and they include
+      your fix in a subsequent release, you can simply drop that
+      single patch when you're updating to the newer release.</para>
 
     <para>Maintaining a single patch against an upstream tree is a
       little tedious and error-prone, but not difficult.  However, the
@@ -146,42 +146,42 @@
       unification of patches and revision control.</para>
 
     <para>A major reason that patches have persisted in the free
-      software and open source world&emdash;in spite of the availability of
-      increasingly capable revision control tools over the years&emdash;is
-      the <emphasis>agility</emphasis> they offer.</para>
+      software and open source world&emdash;in spite of the
+      availability of increasingly capable revision control tools over
+      the years&emdash;is the <emphasis>agility</emphasis> they
+      offer.</para>
 
     <para>Traditional revision control tools make a permanent,
       irreversible record of everything that you do.  While this has
       great value, it's also somewhat stifling.  If you want to
       perform a wild-eyed experiment, you have to be careful in how
       you go about it, or you risk leaving unneeded&emdash;or worse,
-      misleading or destabilising&emdash;traces of your missteps and errors
-      in the permanent revision record.</para>
+      misleading or destabilising&emdash;traces of your missteps and
+      errors in the permanent revision record.</para>
 
     <para>By contrast, MQ's marriage of distributed revision control
       with patches makes it much easier to isolate your work.  Your
       patches live on top of normal revision history, and you can make
       them disappear or reappear at will.  If you don't like a patch,
       you can drop it.  If a patch isn't quite as you want it to be,
-      simply fix it&emdash;as many times as you need to, until you have
-      refined it into the form you desire.</para>
+      simply fix it&emdash;as many times as you need to, until you
+      have refined it into the form you desire.</para>
 
     <para>As an example, the integration of patches with revision
       control makes understanding patches and debugging their
       effects&emdash;and their interplay with the code they're based
-      on&emdash;<emphasis>enormously</emphasis> easier. Since every applied
-      patch has an associated changeset, you can use <command
-	role="hg-cmd">hg log</command> to see which changesets and
-      patches affected a file.  You can use the <literal
-	role="hg-ext">bisect</literal> command to binary-search
-      through all changesets and applied patches to see where a bug
-      got introduced or fixed.  You can use the <command
+      on&emdash;<emphasis>enormously</emphasis> easier. Since every
+      applied patch has an associated changeset, you can give <command
+	role="hg-cmd">hg log</command> a file name to see which
+      changesets and patches affected the file.  You can use the
+      <command role="hg-cmd">hg bisect</command> command to
+      binary-search through all changesets and applied patches to see
+      where a bug got introduced or fixed.  You can use the <command
 	role="hg-cmd">hg annotate</command> command to see which
       changeset or patch modified a particular line of a source file.
       And so on.</para>
 
   </sect1>
-
   <sect1 id="sec:mq:patch">
     <title>Understanding patches</title>
 
@@ -241,7 +241,8 @@
 
     <para>We will return to some of the more subtle aspects of patches
       later (in section <xref linkend="sec:mq:adv-patch"/>), but you
-      should have enough information now to use MQ.</para>
+      should have
+      enough information now to use MQ.</para>
 
   </sect1>
   <sect1 id="sec:mq:start">
@@ -250,15 +251,16 @@
     <para>Because MQ is implemented as an extension, you must
       explicitly enable before you can use it.  (You don't need to
       download anything; MQ ships with the standard Mercurial
-      distribution.)  To enable MQ, edit your <filename role="home">
-	/.hgrc</filename> file, and add the lines below.</para>
+      distribution.)  To enable MQ, edit your <filename
+	role="home">~/.hgrc</filename> file, and add the lines
+      below.</para>
 
     <programlisting>[extensions] hgext.mq =</programlisting>
 
     <para>Once the extension is enabled, it will make a number of new
       commands available.  To verify that the extension is working,
       you can use <command role="hg-cmd">hg help</command> to see if
-      the <command role="hg-ext-mq">hg qinit</command> command is now
+      the <command role="hg-ext-mq">qinit</command> command is now
       available.</para>
 
 <!-- &interaction.mq.qinit-help.help; -->
@@ -266,25 +268,29 @@
     <para>You can use MQ with <emphasis>any</emphasis> Mercurial
       repository, and its commands only operate within that
       repository.  To get started, simply prepare the repository using
-      the <command role="hg-ext-mq">hg qinit</command> command.  This
-      command creates an empty directory called <filename
+      the <command role="hg-ext-mq">qinit</command> command.</para>
+
+<!-- &interaction.mq.tutorial.qinit; -->
+
+    <para>This command creates an empty directory called <filename
 	role="special" class="directory">.hg/patches</filename>, where
       MQ will keep its metadata.  As with many Mercurial commands, the
-      <command role="hg-ext-mq">hg qinit</command> command prints nothing
+      <command role="hg-ext-mq">qinit</command> command prints nothing
       if it succeeds.</para>
-<!-- &interaction.mq.tutorial.qinit; -->
-
 
     <sect2>
       <title>Creating a new patch</title>
 
       <para>To begin work on a new patch, use the <command
-	  role="hg-ext-mq">hg qnew</command> command.  This command takes
-	one argument, the name of the patch to create.  MQ will use
-	this as the name of an actual file in the <filename
-	  role="special" class="directory">.hg/patches</filename>
-	directory, as you can see in figure <xref
-	  linkend="ex:mq:qnew"/>.</para>
+	  role="hg-ext-mq">qnew</command> command.  This command takes
+	one argument, the name of the patch to create.</para>
+
+      <para>MQ will use this as the name of an actual file in the
+	<filename role="special"
+	  class="directory">.hg/patches</filename> directory, as you
+	can see below.</para>
+
+<!-- &interaction.mq.tutorial.qnew; -->
 
       <para>Also newly present in the <filename role="special"
 	  class="directory">.hg/patches</filename> directory are two
@@ -318,18 +324,19 @@
       <title>Refreshing a patch</title>
 
       <para>When you reach a point where you want to save your work,
-	use the <command role="hg-ext-mq">hg qrefresh</command>
-	command to update the patch you are working on.  This command
-	folds the changes you have made in the working directory into
-	your patch, and updates its corresponding changeset to contain
-	those changes.</para>
+	use the <command role="hg-ext-mq">qrefresh</command> command
+	to update the patch you are working on.</para>
 
 <!-- &interaction.mq.tutorial.qrefresh; -->
 
-      <para>You can run <command role="hg-ext-mq">hg hg
-	  qrefresh</command> as often as you like, so it's a good way
-	to <quote>checkpoint</quote> your work.  Refresh your patch at
-	an opportune time; try an experiment; and if the experiment
+      <para>This command folds the changes you have made in the
+	working directory into your patch, and updates its
+	corresponding changeset to contain those changes.</para>
+
+      <para>You can run <command role="hg-ext-mq">qrefresh</command>
+	as often as you like, so it's a good way to
+	<quote>checkpoint</quote> your work.  Refresh your patch at an
+	opportune time; try an experiment; and if the experiment
 	doesn't work out, <command role="hg-cmd">hg revert</command>
 	your modifications back to the last time you refreshed.</para>
 
@@ -340,38 +347,39 @@
       <title>Stacking and tracking patches</title>
 
       <para>Once you have finished working on a patch, or need to work
-	on another, you can use the <command role="hg-ext-mq">hg hg
-	  qnew</command> command again to create a new patch.
-	Mercurial will apply this patch on top of your existing patch.
-	See figure <xref linkend="ex:mq:qnew2"/> for an example.
-	Notice that the patch contains the changes in our prior patch
-	as part of its context (you can see this more clearly in the
-	output of <command role="hg-cmd">hg
+	on another, you can use the <command
+	  role="hg-ext-mq">qnew</command> command again to create a
+	new patch. Mercurial will apply this patch on top of your
+	existing patch.</para>
+
+<!-- &interaction.mq.tutorial.qnew2; -->
+      <para>Notice that the patch contains the changes in our prior
+	patch as part of its context (you can see this more clearly in
+	the output of <command role="hg-cmd">hg
 	  annotate</command>).</para>
 
-<!-- &interaction.mq.tutorial.qnew2; -->
-
       <para>So far, with the exception of <command
-	  role="hg-ext-mq">hg qnew</command> and <command
-	  role="hg-ext-mq">hg qrefresh</command>, we've been careful to
+	  role="hg-ext-mq">qnew</command> and <command
+	  role="hg-ext-mq">qrefresh</command>, we've been careful to
 	only use regular Mercurial commands.  However, MQ provides
 	many commands that are easier to use when you are thinking
-	about patches, as illustrated in figure <xref
-	  linkend="ex:mq:qseries"/>:</para>
+	about patches, as illustrated below.</para>
+
+<!-- &interaction.mq.tutorial.qseries; -->
 
       <itemizedlist>
 	<listitem><para>The <command
-	      role="hg-ext-mq">hg qseries</command> command lists every
+	      role="hg-ext-mq">qseries</command> command lists every
 	    patch that MQ knows about in this repository, from oldest
 	    to newest (most recently
-	    <emphasis>created</emphasis>).</para></listitem>
+	    <emphasis>created</emphasis>).</para>
+	</listitem>
 	<listitem><para>The <command
-	      role="hg-ext-mq">hg qapplied</command> command lists every
+	      role="hg-ext-mq">qapplied</command> command lists every
 	    patch that MQ has <emphasis>applied</emphasis> in this
 	    repository, again from oldest to newest (most recently
-	    applied).</para></listitem></itemizedlist>
-
-<!-- &interaction.mq.tutorial.qseries; -->
+	    applied).</para>
+	</listitem></itemizedlist>
 
     </sect2>
     <sect2>
@@ -386,52 +394,53 @@
 	changeset in the repository, and the effects of the patch and
 	changeset are visible in the working directory.  You can undo
 	the application of a patch using the <command
-	  role="hg-ext-mq">hg qpop</command> command.  MQ still
+	  role="hg-ext-mq">qpop</command> command.  MQ still
 	<emphasis>knows about</emphasis>, or manages, a popped patch,
 	but the patch no longer has a corresponding changeset in the
 	repository, and the working directory does not contain the
 	changes made by the patch.  Figure <xref
-	  linkend="fig:mq:stack"/> illustrates the difference between
-	applied and tracked patches.</para>
+	  linkend="fig:mq:stack"/> illustrates
+	the difference between applied and tracked patches.</para>
 
       <informalfigure id="fig:mq:stack">
-	<mediaobject>
-	  <imageobject><imagedata fileref="mq-stack"/></imageobject>
-	  <textobject><phrase>XXX add text</phrase></textobject>
-	  <caption><para>Applied and unapplied patches in the MQ patch
-	      stack</para></caption>
-	</mediaobject>
+	<mediaobject><imageobject><imagedata
+				    fileref="mq-stack"/></imageobject><textobject><phrase>XXX 
+	      add text</phrase></textobject><caption><para>Applied and
+	      unapplied patches in the MQ patch
+	      stack</para></caption></mediaobject>
       </informalfigure>
 
       <para>You can reapply an unapplied, or popped, patch using the
-	<command role="hg-ext-mq">hg qpush</command> command.  This
+	<command role="hg-ext-mq">qpush</command> command.  This
 	creates a new changeset to correspond to the patch, and the
 	patch's changes once again become present in the working
-	directory.  See figure <xref linkend="ex:mq:qpop"/> for
-	examples of <command role="hg-ext-mq">hg qpop</command> and
-	<command role="hg-ext-mq">hg qpush</command> in action.  Notice
-	that once we have popped a patch or two patches, the output of
-	<command role="hg-ext-mq">hg qseries</command> remains the same,
-	while that of <command role="hg-ext-mq">hg qapplied</command> has
-	changed.</para>
-
+	directory.  See below for examples of <command
+	  role="hg-ext-mq">qpop</command> and <command
+	  role="hg-ext-mq">qpush</command> in action.</para>
 <!-- &interaction.mq.tutorial.qpop; -->
 
+      <para>Notice that once we have popped a patch or two patches,
+	the output of <command role="hg-ext-mq">qseries</command>
+	remains the same, while that of <command
+	  role="hg-ext-mq">qapplied</command> has changed.</para>
+
+
     </sect2>
     <sect2>
       <title>Pushing and popping many patches</title>
 
-      <para>While <command role="hg-ext-mq">hg qpush</command> and
-	<command role="hg-ext-mq">hg qpop</command> each operate on a
+      <para>While <command role="hg-ext-mq">qpush</command> and
+	<command role="hg-ext-mq">qpop</command> each operate on a
 	single patch at a time by default, you can push and pop many
 	patches in one go.  The <option
-	  role="hg-ext-mq-cmd-qpush-opt">-a</option> option to
-	<command role="hg-ext-mq">hg qpush</command> causes it to push
+	  role="hg-ext-mq-cmd-qpush-opt">hg -a</option> option to
+	<command role="hg-ext-mq">qpush</command> causes it to push
 	all unapplied patches, while the <option
 	  role="hg-ext-mq-cmd-qpop-opt">-a</option> option to <command
-	  role="hg-ext-mq">hg qpop</command> causes it to pop all applied
+	  role="hg-ext-mq">qpop</command> causes it to pop all applied
 	patches.  (For some more ways to push and pop many patches,
-	see section <xref linkend="sec:mq:perf"/> below.)</para>
+	see section <xref linkend="sec:mq:perf"/>
+	below.)</para>
 
 <!-- &interaction.mq.tutorial.qpush-a; -->
 
@@ -442,9 +451,9 @@
       <para>Several MQ commands check the working directory before
 	they do anything, and fail if they find any modifications.
 	They do this to ensure that you won't lose any changes that
-	you have made, but not yet incorporated into a patch.  Figure
-	<xref linkend="ex:mq:add"/> illustrates this; the <command
-	  role="hg-ext-mq">hg qnew</command> command will not create a
+	you have made, but not yet incorporated into a patch.  The
+	example below illustrates this; the <command
+	  role="hg-ext-mq">qnew</command> command will not create a
 	new patch if there are outstanding changes, caused in this
 	case by the <command role="hg-cmd">hg add</command> of
 	<filename>file3</filename>.</para>
@@ -456,19 +465,19 @@
 	named <option>-f</option>.  The exact meaning of
 	<option>-f</option> depends on the command.  For example,
 	<command role="hg-cmd">hg qnew <option
-	    role="hg-ext-mq-cmd-qnew-opt">-f</option></command> will
-	incorporate any outstanding changes into the new patch it
+	    role="hg-ext-mq-cmd-qnew-opt">hg -f</option></command>
+	will incorporate any outstanding changes into the new patch it
 	creates, but <command role="hg-cmd">hg qpop <option
-	    role="hg-ext-mq-cmd-qpop-opt">-f</option></command> will
-	revert modifications to any files affected by the patch that
-	it is popping.  Be sure to read the documentation for a
+	    role="hg-ext-mq-cmd-qpop-opt">hg -f</option></command>
+	will revert modifications to any files affected by the patch
+	that it is popping.  Be sure to read the documentation for a
 	command's <option>-f</option> option before you use it!</para>
 
     </sect2>
     <sect2>
       <title>Working on several patches at once</title>
 
-      <para>The <command role="hg-ext-mq">hg qrefresh</command> command
+      <para>The <command role="hg-ext-mq">qrefresh</command> command
 	always refreshes the <emphasis>topmost</emphasis> applied
 	patch.  This means that you can suspend work on one patch (by
 	refreshing it), pop or push to make a different patch the top,
@@ -478,20 +487,19 @@
       <para>Here's an example that illustrates how you can use this
 	ability. Let's say you're developing a new feature as two
 	patches.  The first is a change to the core of your software,
-	and the second&emdash;layered on top of the first&emdash;changes the
-	user interface to use the code you just added to the core.  If
-	you notice a bug in the core while you're working on the UI
-	patch, it's easy to fix the core.  Simply <command
-	  role="hg-ext-mq">hg qrefresh</command> the UI patch to save
-	your in-progress changes, and <command
-	  role="hg-ext-mq">hg qpop</command> down to the core patch.  Fix
-	the core bug, <command role="hg-ext-mq">hg qrefresh</command> the
-	core patch, and <command role="hg-ext-mq">hg qpush</command> back
+	and the second&emdash;layered on top of the
+	first&emdash;changes the user interface to use the code you
+	just added to the core.  If you notice a bug in the core while
+	you're working on the UI patch, it's easy to fix the core.
+	Simply <command role="hg-ext-mq">qrefresh</command> the UI
+	patch to save your in-progress changes, and <command
+	  role="hg-ext-mq">qpop</command> down to the core patch.  Fix
+	the core bug, <command role="hg-ext-mq">qrefresh</command> the
+	core patch, and <command role="hg-ext-mq">qpush</command> back
 	to the UI patch to continue where you left off.</para>
 
     </sect2>
   </sect1>
-
   <sect1 id="sec:mq:adv-patch">
     <title>More about patches</title>
 
@@ -555,19 +563,20 @@
       <para>If you receive a patch from someone that you want to add
 	to your patch queue, and the patch needs a strip count other
 	than one, you cannot just <command
-	  role="hg-ext-mq">hg qimport</command> the patch, because
-	<command role="hg-ext-mq">hg qimport</command> does not yet have
+	  role="hg-ext-mq">qimport</command> the patch, because
+	<command role="hg-ext-mq">qimport</command> does not yet have
 	a <literal>-p</literal> option (see <ulink role="hg-bug"
 	  url="http://www.selenic.com/mercurial/bts/issue311">issue
 	  311</ulink>).  Your best bet is to <command
-	  role="hg-ext-mq">hg qnew</command> a patch of your own, then
+	  role="hg-ext-mq">qnew</command> a patch of your own, then
 	use <command>patch -pN</command> to apply their patch,
 	followed by <command role="hg-cmd">hg addremove</command> to
 	pick up any files added or removed by the patch, followed by
-	<command role="hg-ext-mq">hg qrefresh</command>. This complexity
-	may become unnecessary; see <ulink role="hg-bug"
+	<command role="hg-ext-mq">hg qrefresh</command>. This
+	complexity may become unnecessary; see <ulink role="hg-bug"
 	  url="http://www.selenic.com/mercurial/bts/issue311">issue
-	  311</ulink> for details.</para>
+	  311</ulink> for details.
+      </para>
     </sect2>
     <sect2>
       <title>Strategies for applying a patch</title>
@@ -619,42 +628,39 @@
 
       <para>There are a few useful things to know about how
 	<command>patch</command> works with files.</para>
-
       <itemizedlist>
 	<listitem><para>This should already be obvious, but
 	    <command>patch</command> cannot handle binary
-	    files.</para></listitem>
-
+	    files.</para>
+	</listitem>
 	<listitem><para>Neither does it care about the executable bit;
 	    it creates new files as readable, but not
-	    executable.</para></listitem>
-
+	    executable.</para>
+	</listitem>
 	<listitem><para><command>patch</command> treats the removal of
 	    a file as a diff between the file to be removed and the
 	    empty file.  So your idea of <quote>I deleted this
 	      file</quote> looks like <quote>every line of this file
-	      was deleted</quote> in a patch.</para></listitem>
-
+	      was deleted</quote> in a patch.</para>
+	</listitem>
 	<listitem><para>It treats the addition of a file as a diff
 	    between the empty file and the file to be added.  So in a
 	    patch, your idea of <quote>I added this file</quote> looks
 	    like <quote>every line of this file was
-	      added</quote>.</para></listitem>
-
+	      added</quote>.</para>
+	</listitem>
 	<listitem><para>It treats a renamed file as the removal of the
 	    old name, and the addition of the new name.  This means
 	    that renamed files have a big footprint in patches.  (Note
 	    also that Mercurial does not currently try to infer when
-	    files have been renamed or copied in a
-	    patch.)</para></listitem>
-
+	    files have been renamed or copied in a patch.)</para>
+	</listitem>
 	<listitem><para><command>patch</command> cannot represent
 	    empty files, so you cannot use a patch to represent the
 	    notion <quote>I added this empty file to the
-	      tree</quote>.</para></listitem>
-      </itemizedlist>
-    </sect2>
-
+	      tree</quote>.</para>
+	</listitem></itemizedlist>
+    </sect2>
     <sect2>
       <title>Beware the fuzz</title>
 
@@ -664,7 +670,7 @@
 	file.  The most common cases typically involve applying a
 	patch twice, or at an incorrect location in the file.  If
 	<command>patch</command> or <command
-	  role="hg-ext-mq">hg qpush</command> ever mentions an offset or
+	  role="hg-ext-mq">qpush</command> ever mentions an offset or
 	fuzz factor, you should make sure that the modified files are
 	correct afterwards.</para>
 
@@ -683,7 +689,7 @@
     <sect2>
       <title>Handling rejection</title>
 
-      <para>If <command role="hg-ext-mq">hg qpush</command> fails to
+      <para>If <command role="hg-ext-mq">qpush</command> fails to
 	apply a patch, it will print an error message and exit.  If it
 	has left <filename role="special">.rej</filename> files
 	behind, it is usually best to fix up the rejected hunks before
@@ -692,7 +698,8 @@
       <para>If your patch <emphasis>used to</emphasis> apply cleanly,
 	and no longer does because you've changed the underlying code
 	that your patches are based on, Mercurial Queues can help; see
-	section <xref linkend="sec:mq:merge"/> for details.</para>
+	section <xref
+	  linkend="sec:mq:merge"/> for details.</para>
 
       <para>Unfortunately, there aren't any great techniques for
 	dealing with rejected hunks.  Most often, you'll need to view
@@ -715,19 +722,18 @@
 
       <itemizedlist>
 	<listitem><para>The context in the middle of a hunk has
-	    changed.</para></listitem>
-
+	    changed.</para>
+	</listitem>
 	<listitem><para>A hunk is missing some context at the
-	    beginning or end.</para></listitem>
-
+	    beginning or end.</para>
+	</listitem>
 	<listitem><para>A large hunk might apply better&emdash;either
-	    entirely or in part&emdash;if it was broken up into smaller
-	    hunks.</para></listitem>
-
+	    entirely or in part&emdash;if it was broken up into
+	    smaller hunks.</para>
+	</listitem>
 	<listitem><para>A hunk removes lines with slightly different
-	    content than those currently present in the
-	    file.</para></listitem>
-      </itemizedlist>
+	    content than those currently present in the file.</para>
+	</listitem></itemizedlist>
 
       <para>If you use <command>wiggle</command> or
 	<command>mpatch</command>, you should be doubly careful to
@@ -754,12 +760,12 @@
 
     <para>On my old, slow laptop, I was able to <command
 	role="hg-cmd">hg qpush <option
-	  role="hg-ext-mq-cmd-qpush-opt">-a</option></command> all
+	  role="hg-ext-mq-cmd-qpush-opt">hg -a</option></command> all
       1,738 patches in 3.5 minutes, and <command role="hg-cmd">hg qpop
-	<option role="hg-ext-mq-cmd-qpop-opt">-a</option></command>
+	<option role="hg-ext-mq-cmd-qpop-opt">hg -a</option></command>
       them all in 30 seconds.  (On a newer laptop, the time to push
       all patches dropped to two minutes.)  I could <command
-	role="hg-ext-mq">hg qrefresh</command> one of the biggest patches
+	role="hg-ext-mq">qrefresh</command> one of the biggest patches
       (which made 22,779 lines of changes to 287 files) in 6.6
       seconds.</para>
 
@@ -769,23 +775,23 @@
 
     <para>First of all, try to <quote>batch</quote> operations
       together.  Every time you run <command
-	role="hg-ext-mq">hg qpush</command> or <command
-	role="hg-ext-mq">hg qpop</command>, these commands scan the
+	role="hg-ext-mq">qpush</command> or <command
+	role="hg-ext-mq">qpop</command>, these commands scan the
       working directory once to make sure you haven't made some
       changes and then forgotten to run <command
-	role="hg-ext-mq">hg qrefresh</command>.  On a small tree, the
+	role="hg-ext-mq">qrefresh</command>.  On a small tree, the
       time that this scan takes is unnoticeable.  However, on a
       medium-sized tree (containing tens of thousands of files), it
       can take a second or more.</para>
 
-    <para>The <command role="hg-ext-mq">hg qpush</command> and <command
-	role="hg-ext-mq">hg qpop</command> commands allow you to push and
+    <para>The <command role="hg-ext-mq">qpush</command> and <command
+	role="hg-ext-mq">qpop</command> commands allow you to push and
       pop multiple patches at a time.  You can identify the
       <quote>destination patch</quote> that you want to end up at.
-      When you <command role="hg-ext-mq">hg qpush</command> with a
+      When you <command role="hg-ext-mq">qpush</command> with a
       destination specified, it will push patches until that patch is
       at the top of the applied stack.  When you <command
-	role="hg-ext-mq">hg qpop</command> to a destination, MQ will pop
+	role="hg-ext-mq">qpop</command> to a destination, MQ will pop
       patches until the destination patch is at the top.</para>
 
     <para>You can identify a destination patch using either the name
@@ -794,7 +800,6 @@
       is zero, the second is one, and so on.</para>
 
   </sect1>
-
   <sect1 id="sec:mq:merge">
     <title>Updating your patches when the underlying code
       changes</title>
@@ -809,15 +814,14 @@
       series.</para>
 
     <para>The simplest way to do this is to <command role="hg-cmd">hg
-	qpop <option
-	  role="hg-ext-mq-cmd-qpop-opt">-a</option></command> your
-      patches, then <command role="hg-cmd">hg pull</command> changes
-      into the underlying repository, and finally <command
-	role="hg-cmd">hg qpush <option
-	  role="hg-ext-mq-cmd-qpop-opt">-a</option></command> your
+	qpop <option role="hg-ext-mq-cmd-qpop-opt">hg
+	  -a</option></command> your patches, then <command
+	role="hg-cmd">hg pull</command> changes into the underlying
+      repository, and finally <command role="hg-cmd">hg qpush <option
+	  role="hg-ext-mq-cmd-qpop-opt">hg -a</option></command> your
       patches again.  MQ will stop pushing any time it runs across a
       patch that fails to apply during conflicts, allowing you to fix
-      your conflicts, <command role="hg-ext-mq">hg qrefresh</command> the
+      your conflicts, <command role="hg-ext-mq">qrefresh</command> the
       affected patch, and continue pushing until you have fixed your
       entire stack.</para>
 
@@ -828,8 +832,8 @@
       fixing up rejected hunks by hand quickly becomes
       tiresome.</para>
 
-    <para>It's possible to partially automate the rebasing process. If
-      your patches apply cleanly against some revision of the
+    <para>It's possible to partially automate the rebasing process.
+      If your patches apply cleanly against some revision of the
       underlying repo, MQ can use this information to help you to
       resolve conflicts between your patches and a different
       revision.</para>
@@ -838,12 +842,12 @@
     <orderedlist>
       <listitem><para>To begin, <command role="hg-cmd">hg qpush
 	    -a</command> all of your patches on top of the revision
-	  where you know that they apply cleanly.</para></listitem>
-
+	  where you know that they apply cleanly.</para>
+      </listitem>
       <listitem><para>Save a backup copy of your patch directory using
 	  <command role="hg-cmd">hg qsave <option
-	      role="hg-ext-mq-cmd-qsave-opt">-e</option> <option
-	      role="hg-ext-mq-cmd-qsave-opt">-c</option></command>.
+	      role="hg-ext-mq-cmd-qsave-opt">hg -e</option> <option
+	      role="hg-ext-mq-cmd-qsave-opt">hg -c</option></command>.
 	  This prints the name of the directory that it has saved the
 	  patches in.  It will save the patches to a directory called
 	  <filename role="special"
@@ -852,36 +856,34 @@
 	  <quote>save changeset</quote> on top of your applied
 	  patches; this is for internal book-keeping, and records the
 	  states of the <filename role="special">series</filename> and
-	  <filename role="special">status</filename>
-	  files.</para></listitem>
-
-      <listitem>
-	<para>Use <command role="hg-cmd">hg pull</command> to bring
-	  new changes into the underlying repository.  (Don't run
-	  <command role="hg-cmd">hg pull -u</command>; see below for
-	  why.)</para></listitem>
-
+	  <filename role="special">status</filename> files.</para>
+      </listitem>
+      <listitem><para>Use <command role="hg-cmd">hg pull</command> to
+	  bring new changes into the underlying repository.  (Don't
+	  run <command role="hg-cmd">hg pull -u</command>; see below
+	  for why.)</para>
+      </listitem>
       <listitem><para>Update to the new tip revision, using <command
 	    role="hg-cmd">hg update <option
 	      role="hg-opt-update">-C</option></command> to override
-	  the patches you have pushed.</para></listitem>
-
+	  the patches you have pushed.</para>
+      </listitem>
       <listitem><para>Merge all patches using
-	  \hgcmdargs{qpush}{<option
-	    role="hg-ext-mq-cmd-qpush-opt">-m</option> <option
-	    role="hg-ext-mq-cmd-qpush-opt">-a</option>}.  The <option
-	    role="hg-ext-mq-cmd-qpush-opt">-m</option> option to
-	  <command role="hg-ext-mq">hg qpush</command> tells MQ to
+	  \hgcmdargs{qpush}{<option role="hg-ext-mq-cmd-qpush-opt">hg
+	    -m</option> <option role="hg-ext-mq-cmd-qpush-opt">hg
+	    -a</option>}.  The <option
+	    role="hg-ext-mq-cmd-qpush-opt">hg -m</option> option to
+	  <command role="hg-ext-mq">qpush</command> tells MQ to
 	  perform a three-way merge if the patch fails to
-	  apply.</para></listitem>
-    </orderedlist>
+	  apply.</para>
+      </listitem></orderedlist>
 
     <para>During the <command role="hg-cmd">hg qpush <option
-	  role="hg-ext-mq-cmd-qpush-opt">-m</option></command>, each
-      patch in the <filename role="special">series</filename> file is
-      applied normally.  If a patch applies with fuzz or rejects, MQ
-      looks at the queue you <command
-	role="hg-ext-mq">hg qsave</command>d, and performs a three-way
+	  role="hg-ext-mq-cmd-qpush-opt">hg -m</option></command>,
+      each patch in the <filename role="special">series</filename>
+      file is applied normally.  If a patch applies with fuzz or
+      rejects, MQ looks at the queue you <command
+	role="hg-ext-mq">qsave</command>d, and performs a three-way
       merge with the corresponding changeset.  This merge uses
       Mercurial's normal merge machinery, so it may pop up a GUI merge
       tool to help you to resolve problems.</para>
@@ -893,9 +895,7 @@
       extra head from the old patch queue, and a copy of the old patch
       queue will be in <filename role="special"
 	class="directory">.hg/patches.N</filename>. You can remove the
-      extra head using <command role="hg-cmd">hg qpop <option
-	  role="hg-ext-mq-cmd-qpop-opt">-a</option> <option
-	  role="hg-ext-mq-cmd-qpop-opt">-n</option>
+      extra head using <command role="hg-cmd">hg qpop -a -n
 	patches.N</command> or <command role="hg-cmd">hg
 	strip</command>.  You can delete <filename role="special"
 	class="directory">.hg/patches.N</filename> once you are sure
@@ -908,7 +908,7 @@
     <para>MQ commands that work with patches let you refer to a patch
       either by using its name or by a number.  By name is obvious
       enough; pass the name <filename>foo.patch</filename> to <command
-	role="hg-ext-mq">hg qpush</command>, for example, and it will
+	role="hg-ext-mq">qpush</command>, for example, and it will
       push patches until <filename>foo.patch</filename> is
       applied.</para>
 
@@ -920,7 +920,7 @@
 
     <para>Referring to a patch by index isn't much different.  The
       first patch printed in the output of <command
-	role="hg-ext-mq">hg qseries</command> is patch zero (yes, it's
+	role="hg-ext-mq">qseries</command> is patch zero (yes, it's
       one of those start-at-zero counting systems); the second is
       patch one; and so on.</para>
 
@@ -941,19 +941,18 @@
     <itemizedlist>
       <listitem><para>Want to patchbomb a mailing list with your
 	  latest series of changes?</para>
-	<programlisting>
-	  hg email qbase:qtip
-	</programlisting></listitem>
-      <listitem><para>  (Don't know what <quote>patchbombing</quote>
-	  is?  See section <xref
-	    linkend="sec:hgext:patchbomb"/>.)</para></listitem>
-
+	<programlisting>hg email qbase:qtip
+	</programlisting>
+	<para>  (Don't know what <quote>patchbombing</quote> is?  See
+	  section <xref linkend="sec:hgext:patchbomb"/>.)</para>
+      </listitem>
       <listitem><para>Need to see all of the patches since
 	  <literal>foo.patch</literal> that have touched files in a
 	  subdirectory of your tree?</para>
 	<programlisting>
 	  hg log -r foo.patch:qtip <emphasis>subdir</emphasis>
-	</programlisting></listitem>
+	</programlisting>
+      </listitem>
     </itemizedlist>
 
     <para>Because MQ makes the names of patches available to the rest
@@ -961,16 +960,16 @@
       don't need to type in the entire name of a patch when you want
       to identify it by name.</para>
 
-<!-- &interaction.mq.id.output; -->
-
     <para>Another nice consequence of representing patch names as tags
       is that when you run the <command role="hg-cmd">hg log</command>
       command, it will display a patch's name as a tag, simply as part
       of its normal output.  This makes it easy to visually
       distinguish applied patches from underlying
-      <quote>normal</quote> revisions.  Figure <xref
-	linkend="ex:mq:id"/> shows a few normal Mercurial commands in
-      use with applied patches.</para>
+      <quote>normal</quote> revisions.  The following example shows a
+      few normal Mercurial commands in use with applied
+      patches.</para>
+
+<!-- &interaction.mq.id.output; -->
 
   </sect1>
   <sect1>
@@ -982,25 +981,24 @@
 
     <itemizedlist>
       <listitem><para>Normally, when you <command
-	    role="hg-ext-mq">hg qpop</command> a patch and <command
-	    role="hg-ext-mq">hg qpush</command> it again, the changeset
+	    role="hg-ext-mq">qpop</command> a patch and <command
+	    role="hg-ext-mq">qpush</command> it again, the changeset
 	  that represents the patch after the pop/push will have a
 	  <emphasis>different identity</emphasis> than the changeset
 	  that represented the hash beforehand.  See section <xref
-	    linkend="sec:mqref:cmd:qpush"/> for information as to why
-	  this is.</para></listitem>
-
+	    linkend="sec:mqref:cmd:qpush"/> for
+	  information as to why this is.</para>
+      </listitem>
       <listitem><para>It's not a good idea to <command
 	    role="hg-cmd">hg merge</command> changes from another
 	  branch with a patch changeset, at least if you want to
 	  maintain the <quote>patchiness</quote> of that changeset and
 	  changesets below it on the patch stack.  If you try to do
 	  this, it will appear to succeed, but MQ will become
-	  confused.</para></listitem>
-    </itemizedlist>
-
-  </sect1>
-
+	  confused.</para>
+      </listitem></itemizedlist>
+
+  </sect1>
   <sect1 id="sec:mq:repo">
     <title>Managing patches in a repository</title>
 
@@ -1014,7 +1012,7 @@
       contents of the patch directory as a Mercurial repository in its
       own right.  This can be a useful way to work.  For example, you
       can work on a patch for a while, <command
-	role="hg-ext-mq">hg qrefresh</command> it, then <command
+	role="hg-ext-mq">qrefresh</command> it, then <command
 	role="hg-cmd">hg commit</command> the current state of the
       patch.  This lets you <quote>roll back</quote> to that version
       of the patch later on.</para>
@@ -1040,25 +1038,24 @@
       <para>MQ helps you to work with the <filename role="special"
 	  class="directory">.hg/patches</filename> directory as a
 	repository; when you prepare a repository for working with
-	patches using <command role="hg-ext-mq">hg qinit</command>, you
-	can pass the <option
-	  role="hg-ext-mq-cmd-qinit-opt">-c</option> option to create
-	the <filename role="special"
+	patches using <command role="hg-ext-mq">qinit</command>, you
+	can pass the <option role="hg-ext-mq-cmd-qinit-opt">hg
+	  -c</option> option to create the <filename role="special"
 	  class="directory">.hg/patches</filename> directory as a
 	Mercurial repository.</para>
 
       <note>
 	<para>  If you forget to use the <option
-	    role="hg-ext-mq-cmd-qinit-opt">-c</option> option, you can
-	  simply go into the <filename role="special"
+	    role="hg-ext-mq-cmd-qinit-opt">hg -c</option> option, you
+	  can simply go into the <filename role="special"
 	    class="directory">.hg/patches</filename> directory at any
-	  time and run <command role="hg-cmd">hg init</command>. Don't
-	  forget to add an entry for the <filename
+	  time and run <command role="hg-cmd">hg init</command>.
+	  Don't forget to add an entry for the <filename
 	    role="special">status</filename> file to the <filename
 	    role="special">.hgignore</filename> file, though</para>
 
 	<para>  (<command role="hg-cmd">hg qinit <option
-	      role="hg-ext-mq-cmd-qinit-opt">-c</option></command>
+	      role="hg-ext-mq-cmd-qinit-opt">hg -c</option></command>
 	  does this for you automatically); you
 	  <emphasis>really</emphasis> don't want to manage the
 	  <filename role="special">status</filename> file.</para>
@@ -1070,7 +1067,7 @@
 	  add</command> every patch that you create and import.</para>
 
       <para>MQ provides a shortcut command, <command
-	  role="hg-ext-mq">hg qcommit</command>, that runs <command
+	  role="hg-ext-mq">qcommit</command>, that runs <command
 	  role="hg-cmd">hg commit</command> in the <filename
 	  role="special" class="directory">.hg/patches</filename>
 	directory.  This saves some bothersome typing.</para>
@@ -1079,12 +1076,11 @@
 	you can define the alias <command>mq</command> on Unix
 	systems. For example, on Linux systems using the
 	<command>bash</command> shell, you can include the following
-	snippet in your <filename role="home">
-	  /.bashrc</filename>.</para>
-
-      <programlisting>
-	alias mq=`hg -R $(hg root)/.hg/patches'
-      </programlisting>
+	snippet in your <filename
+	  role="home">~/.bashrc</filename>.</para>
+
+      <programlisting>alias mq=`hg -R $(hg
+	root)/.hg/patches'</programlisting>
 
       <para>You can then issue commands of the form <command>mq
 	  pull</command> from the main repository.</para>
@@ -1102,9 +1098,9 @@
 	  update</command> changes to patches or the <filename
 	  role="special">series</filename> file, you will have to
 	<command role="hg-cmd">hg qpop <option
-	    role="hg-ext-mq-cmd-qpop-opt">-a</option></command> and
+	    role="hg-ext-mq-cmd-qpop-opt">hg -a</option></command> and
 	then <command role="hg-cmd">hg qpush <option
-	    role="hg-ext-mq-cmd-qpush-opt">-a</option></command> in
+	    role="hg-ext-mq-cmd-qpush-opt">hg -a</option></command> in
 	the underlying repository to see those changes show up there.
 	If you forget to do this, you can confuse MQ's idea of which
 	patches are applied.</para>
@@ -1121,9 +1117,9 @@
     <para>The <command>diffstat</command> command
       <citation>web:diffstat</citation> generates a histogram of the
       modifications made to each file in a patch.  It provides a good
-      way to <quote>get a sense of</quote> a patch&emdash;which files it
-      affects, and how much change it introduces to each file and as a
-      whole.  (I find that it's a good idea to use
+      way to <quote>get a sense of</quote> a patch&emdash;which files
+      it affects, and how much change it introduces to each file and
+      as a whole.  (I find that it's a good idea to use
       <command>diffstat</command>'s <option
 	role="cmd-opt-diffstat">-p</option> option as a matter of
       course, as otherwise it will try to do clever things with
@@ -1162,30 +1158,30 @@
       the patch is.  Long names shouldn't be a problem; you won't be
       typing the names often, but you <emphasis>will</emphasis> be
       running commands like <command
-	role="hg-ext-mq">hg qapplied</command> and <command
-	role="hg-ext-mq">hg qtop</command> over and over. Good naming
+	role="hg-ext-mq">qapplied</command> and <command
+	role="hg-ext-mq">qtop</command> over and over. Good naming
       becomes especially important when you have a number of patches
       to work with, or if you are juggling a number of different tasks
       and your patches only get a fraction of your attention.</para>
 
     <para>Be aware of what patch you're working on.  Use the <command
-	role="hg-ext-mq">hg qtop</command> command and skim over the text
+	role="hg-ext-mq">qtop</command> command and skim over the text
       of your patches frequently&emdash;for example, using <command
 	role="hg-cmd">hg tip <option
-	  role="hg-opt-tip">-p</option></command>)&emdash;to be sure of
-      where you stand.  I have several times worked on and <command
-	role="hg-ext-mq">hg qrefresh</command>ed a patch other than the
+	  role="hg-opt-tip">-p</option></command>)&emdash;to be sure
+      of where you stand.  I have several times worked on and <command
+	role="hg-ext-mq">qrefresh</command>ed a patch other than the
       one I intended, and it's often tricky to migrate changes into
       the right patch after making them in the wrong one.</para>
 
     <para>For this reason, it is very much worth investing a little
       time to learn how to use some of the third-party tools I
       described in section <xref linkend="sec:mq:tools"/>,
-      particularly <command>diffstat</command> and
-      <command>filterdiff</command>. The former will give you a quick
-      idea of what changes your patch is making, while the latter
-      makes it easy to splice hunks selectively out of one patch and
-      into another.</para>
+      particularly
+      <command>diffstat</command> and <command>filterdiff</command>.
+      The former will give you a quick idea of what changes your patch
+      is making, while the latter makes it easy to splice hunks
+      selectively out of one patch and into another.</para>
 
   </sect1>
   <sect1>
@@ -1225,7 +1221,7 @@
       <title>Combining entire patches</title>
 
       <para>MQ provides a command, <command
-	  role="hg-ext-mq">hg qfold</command> that lets you combine
+	  role="hg-ext-mq">qfold</command> that lets you combine
 	entire patches.  This <quote>folds</quote> the patches you
 	name, in the order you name them, into the topmost applied
 	patch, and concatenates their descriptions onto the end of its
@@ -1234,7 +1230,7 @@
 
       <para>The order in which you fold patches matters.  If your
 	topmost applied patch is <literal>foo</literal>, and you
-	<command role="hg-ext-mq">hg qfold</command>
+	<command role="hg-ext-mq">qfold</command>
 	<literal>bar</literal> and <literal>quux</literal> into it,
 	you will end up with a patch that has the same effect as if
 	you applied first <literal>foo</literal>, then
@@ -1257,9 +1253,9 @@
 	output onto the end of the patch you want to merge into.  You
 	usually won't need to modify the patch you've merged the
 	changes from.  Instead, MQ will report some rejected hunks
-	when you <command role="hg-ext-mq">hg qpush</command> it (from
+	when you <command role="hg-ext-mq">qpush</command> it (from
 	the hunks you moved into the other patch), and you can simply
-	<command role="hg-ext-mq">hg qrefresh</command> the patch to drop
+	<command role="hg-ext-mq">qrefresh</command> the patch to drop
 	the duplicate hunks.</para>
 
       <para>If you have a patch that has multiple hunks modifying a
@@ -1273,16 +1269,14 @@
       <itemizedlist>
 	<listitem><para>(in the first column) a <emphasis>file
 	      number</emphasis> to identify each file modified in the
-	    patch;</para></listitem>
-
+	    patch;</para>
+	</listitem>
 	<listitem><para>(on the next line, indented) the line number
-	    within a modified file where a hunk starts;
-	    and</para></listitem>
-
+	    within a modified file where a hunk starts; and</para>
+	</listitem>
 	<listitem><para>(on the same line) a <emphasis>hunk
-	      number</emphasis> to identify that
-	    hunk.</para></listitem>
-      </itemizedlist>
+	      number</emphasis> to identify that hunk.</para>
+	</listitem></itemizedlist>
 
       <para>You'll have to use some visual inspection, and reading of
 	the patch, to identify the file and hunk numbers you'll want,
diff -r 8631da51309b -r b90b024729f1 en/ch13-mq-collab.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch13-mq-collab.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,496 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:mq-collab">
+  <title>Advanced uses of Mercurial Queues</title>
+
+  <para>While it's easy to pick up straightforward uses of Mercurial
+    Queues, use of a little discipline and some of MQ's less
+    frequently used capabilities makes it possible to work in
+    complicated development environments.</para>
+
+  <para>In this chapter, I will use as an example a technique I have
+    used to manage the development of an Infiniband device driver for
+    the Linux kernel.  The driver in question is large (at least as
+    drivers go), with 25,000 lines of code spread across 35 source
+    files.  It is maintained by a small team of developers.</para>
+
+  <para>While much of the material in this chapter is specific to
+    Linux, the same principles apply to any code base for which you're
+    not the primary owner, and upon which you need to do a lot of
+    development.</para>
+
+  <sect1>
+    <title>The problem of many targets</title>
+
+    <para>The Linux kernel changes rapidly, and has never been
+      internally stable; developers frequently make drastic changes
+      between releases. This means that a version of the driver that
+      works well with a particular released version of the kernel will
+      not even <emphasis>compile</emphasis> correctly against,
+      typically, any other version.</para>
+
+    <para>To maintain a driver, we have to keep a number of distinct
+      versions of Linux in mind.</para>
+    <itemizedlist>
+      <listitem><para>One target is the main Linux kernel development
+	  tree. Maintenance of the code is in this case partly shared
+	  by other developers in the kernel community, who make
+	  <quote>drive-by</quote> modifications to the driver as they
+	  develop and refine kernel subsystems.</para>
+      </listitem>
+      <listitem><para>We also maintain a number of
+	  <quote>backports</quote> to older versions of the Linux
+	  kernel, to support the needs of customers who are running
+	  older Linux distributions that do not incorporate our
+	  drivers.  (To <emphasis>backport</emphasis> a piece of code
+	  is to modify it to work in an older version of its target
+	  environment than the version it was developed for.)</para>
+      </listitem>
+      <listitem><para>Finally, we make software releases on a schedule
+	  that is necessarily not aligned with those used by Linux
+	  distributors and kernel developers, so that we can deliver
+	  new features to customers without forcing them to upgrade
+	  their entire kernels or distributions.</para>
+      </listitem></itemizedlist>
+
+    <sect2>
+      <title>Tempting approaches that don't work well</title>
+
+      <para>There are two <quote>standard</quote> ways to maintain a
+	piece of software that has to target many different
+	environments.</para>
+
+      <para>The first is to maintain a number of branches, each
+	intended for a single target.  The trouble with this approach
+	is that you must maintain iron discipline in the flow of
+	changes between repositories. A new feature or bug fix must
+	start life in a <quote>pristine</quote> repository, then
+	percolate out to every backport repository.  Backport changes
+	are more limited in the branches they should propagate to; a
+	backport change that is applied to a branch where it doesn't
+	belong will probably stop the driver from compiling.</para>
+
+      <para>The second is to maintain a single source tree filled with
+	conditional statements that turn chunks of code on or off
+	depending on the intended target.  Because these
+	<quote>ifdefs</quote> are not allowed in the Linux kernel
+	tree, a manual or automatic process must be followed to strip
+	them out and yield a clean tree.  A code base maintained in
+	this fashion rapidly becomes a rat's nest of conditional
+	blocks that are difficult to understand and maintain.</para>
+
+      <para>Neither of these approaches is well suited to a situation
+	where you don't <quote>own</quote> the canonical copy of a
+	source tree.  In the case of a Linux driver that is
+	distributed with the standard kernel, Linus's tree contains
+	the copy of the code that will be treated by the world as
+	canonical.  The upstream version of <quote>my</quote> driver
+	can be modified by people I don't know, without me even
+	finding out about it until after the changes show up in
+	Linus's tree.</para>
+
+      <para>These approaches have the added weakness of making it
+	difficult to generate well-formed patches to submit
+	upstream.</para>
+
+      <para>In principle, Mercurial Queues seems like a good candidate
+	to manage a development scenario such as the above.  While
+	this is indeed the case, MQ contains a few added features that
+	make the job more pleasant.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Conditionally applying patches with guards</title>
+
+    <para>Perhaps the best way to maintain sanity with so many targets
+      is to be able to choose specific patches to apply for a given
+      situation.  MQ provides a feature called <quote>guards</quote>
+      (which originates with quilt's <literal>guards</literal>
+      command) that does just this.  To start off, let's create a
+      simple repository for experimenting in. <!--
+      &interaction.mq.guards.init; --> This gives us a tiny repository
+      that contains two patches that don't have any dependencies on
+      each other, because they touch different files.</para>
+
+    <para>The idea behind conditional application is that you can
+      <quote>tag</quote> a patch with a <emphasis>guard</emphasis>,
+      which is simply a text string of your choosing, then tell MQ to
+      select specific guards to use when applying patches.  MQ will
+      then either apply, or skip over, a guarded patch, depending on
+      the guards that you have selected.</para>
+
+    <para>A patch can have an arbitrary number of guards; each one is
+      <emphasis>positive</emphasis> (<quote>apply this patch if this
+	guard is selected</quote>) or <emphasis>negative</emphasis>
+      (<quote>skip this patch if this guard is selected</quote>).  A
+      patch with no guards is always applied.</para>
+
+  </sect1>
+  <sect1>
+    <title>Controlling the guards on a patch</title>
+
+    <para>The <command role="hg-ext-mq">qguard</command> command lets
+      you determine which guards should apply to a patch, or display
+      the guards that are already in effect. Without any arguments, it
+      displays the guards on the current topmost patch. <!--
+      &interaction.mq.guards.qguard; --> To set a positive guard on a
+      patch, prefix the name of the guard with a
+      <quote><literal>+</literal></quote>. <!--
+      &interaction.mq.guards.qguard.pos; --> To set a negative guard
+      on a patch, prefix the name of the guard with a
+      <quote><literal>-</literal></quote>. <!--
+      &interaction.mq.guards.qguard.neg; --></para>
+
+    <note>
+      <para>  The <command role="hg-ext-mq">qguard</command> command
+	<emphasis>sets</emphasis> the guards on a patch; it doesn't
+	<emphasis>modify</emphasis> them.  What this means is that if
+	you run <command role="hg-cmd">hg qguard +a +b</command> on a
+	patch, then <command role="hg-cmd">hg qguard +c</command> on
+	the same patch, the <emphasis>only</emphasis> guard that will
+	be set on it afterwards is <literal>+c</literal>.</para>
+    </note>
+
+    <para>Mercurial stores guards in the <filename
+	role="special">series</filename> file; the form in which they
+      are stored is easy both to understand and to edit by hand. (In
+      other words, you don't have to use the <command
+	role="hg-ext-mq">qguard</command> command if you don't want
+      to; it's okay to simply edit the <filename
+	role="special">series</filename> file.) <!--
+      &interaction.mq.guards.series; --></para>
+
+  </sect1>
+  <sect1>
+    <title>Selecting the guards to use</title>
+
+    <para>The <command role="hg-ext-mq">qselect</command> command
+      determines which guards are active at a given time.  The effect
+      of this is to determine which patches MQ will apply the next
+      time you run <command role="hg-ext-mq">qpush</command>.  It has
+      no other effect; in particular, it doesn't do anything to
+      patches that are already applied.</para>
+
+    <para>With no arguments, the <command
+	role="hg-ext-mq">qselect</command> command lists the guards
+      currently in effect, one per line of output.  Each argument is
+      treated as the name of a guard to apply. <!--
+      &interaction.mq.guards.qselect.foo; --> In case you're
+      interested, the currently selected guards are stored in the
+      <filename role="special">guards</filename> file. <!--
+      &interaction.mq.guards.qselect.cat; --> We can see the effect
+      the selected guards have when we run <command
+	role="hg-ext-mq">qpush</command>. <!--
+      &interaction.mq.guards.qselect.qpush; --></para>
+
+    <para>A guard cannot start with a
+      <quote><literal>+</literal></quote> or
+      <quote><literal>-</literal></quote> character.  The name of a
+      guard must not contain white space, but most other characters
+      are acceptable.  If you try to use a guard with an invalid name,
+      MQ will complain: <!-- &interaction.mq.guards.qselect.error; -->
+      Changing the selected guards changes the patches that are
+      applied. <!-- &interaction.mq.guards.qselect.quux; --> You can
+      see in the example below that negative guards take precedence
+      over positive guards. <!--
+      &interaction.mq.guards.qselect.foobar; --></para>
+
+  </sect1>
+  <sect1>
+    <title>MQ's rules for applying patches</title>
+
+    <para>The rules that MQ uses when deciding whether to apply a
+      patch are as follows.</para>
+    <itemizedlist>
+      <listitem><para>A patch that has no guards is always
+	  applied.</para>
+      </listitem>
+      <listitem><para>If the patch has any negative guard that matches
+	  any currently selected guard, the patch is skipped.</para>
+      </listitem>
+      <listitem><para>If the patch has any positive guard that matches
+	  any currently selected guard, the patch is applied.</para>
+      </listitem>
+      <listitem><para>If the patch has positive or negative guards,
+	  but none matches any currently selected guard, the patch is
+	  skipped.</para>
+      </listitem></itemizedlist>
+
+  </sect1>
+  <sect1>
+    <title>Trimming the work environment</title>
+
+    <para>In working on the device driver I mentioned earlier, I don't
+      apply the patches to a normal Linux kernel tree.  Instead, I use
+      a repository that contains only a snapshot of the source files
+      and headers that are relevant to Infiniband development.  This
+      repository is 1% the size of a kernel repository, so it's easier
+      to work with.</para>
+
+    <para>I then choose a <quote>base</quote> version on top of which
+      the patches are applied.  This is a snapshot of the Linux kernel
+      tree as of a revision of my choosing.  When I take the snapshot,
+      I record the changeset ID from the kernel repository in the
+      commit message.  Since the snapshot preserves the
+      <quote>shape</quote> and content of the relevant parts of the
+      kernel tree, I can apply my patches on top of either my tiny
+      repository or a normal kernel tree.</para>
+
+    <para>Normally, the base tree atop which the patches apply should
+      be a snapshot of a very recent upstream tree.  This best
+      facilitates the development of patches that can easily be
+      submitted upstream with few or no modifications.</para>
+
+  </sect1>
+  <sect1>
+    <title>Dividing up the <filename role="special">series</filename>
+      file</title>
+
+    <para>I categorise the patches in the <filename
+	role="special">series</filename> file into a number of logical
+      groups.  Each section of like patches begins with a block of
+      comments that describes the purpose of the patches that
+      follow.</para>
+
+    <para>The sequence of patch groups that I maintain follows.  The
+      ordering of these groups is important; I'll describe why after I
+      introduce the groups.</para>
+    <itemizedlist>
+      <listitem><para>The <quote>accepted</quote> group.  Patches that
+	  the development team has submitted to the maintainer of the
+	  Infiniband subsystem, and which he has accepted, but which
+	  are not present in the snapshot that the tiny repository is
+	  based on.  These are <quote>read only</quote> patches,
+	  present only to transform the tree into a similar state as
+	  it is in the upstream maintainer's repository.</para>
+      </listitem>
+      <listitem><para>The <quote>rework</quote> group.  Patches that I
+	  have submitted, but that the upstream maintainer has
+	  requested modifications to before he will accept
+	  them.</para>
+      </listitem>
+      <listitem><para>The <quote>pending</quote> group.  Patches that
+	  I have not yet submitted to the upstream maintainer, but
+	  which we have finished working on. These will be <quote>read
+	    only</quote> for a while.  If the upstream maintainer
+	  accepts them upon submission, I'll move them to the end of
+	  the <quote>accepted</quote> group.  If he requests that I
+	  modify any, I'll move them to the beginning of the
+	  <quote>rework</quote> group.</para>
+      </listitem>
+      <listitem><para>The <quote>in progress</quote> group.  Patches
+	  that are actively being developed, and should not be
+	  submitted anywhere yet.</para>
+      </listitem>
+      <listitem><para>The <quote>backport</quote> group.  Patches that
+	  adapt the source tree to older versions of the kernel
+	  tree.</para>
+      </listitem>
+      <listitem><para>The <quote>do not ship</quote> group.  Patches
+	  that for some reason should never be submitted upstream.
+	  For example, one such patch might change embedded driver
+	  identification strings to make it easier to distinguish, in
+	  the field, between an out-of-tree version of the driver and
+	  a version shipped by a distribution vendor.</para>
+      </listitem></itemizedlist>
+
+    <para>Now to return to the reasons for ordering groups of patches
+      in this way.  We would like the lowest patches in the stack to
+      be as stable as possible, so that we will not need to rework
+      higher patches due to changes in context.  Putting patches that
+      will never be changed first in the <filename
+	role="special">series</filename> file serves this
+      purpose.</para>
+
+    <para>We would also like the patches that we know we'll need to
+      modify to be applied on top of a source tree that resembles the
+      upstream tree as closely as possible.  This is why we keep
+      accepted patches around for a while.</para>
+
+    <para>The <quote>backport</quote> and <quote>do not ship</quote>
+      patches float at the end of the <filename
+	role="special">series</filename> file.  The backport patches
+      must be applied on top of all other patches, and the <quote>do
+	not ship</quote> patches might as well stay out of harm's
+      way.</para>
+
+  </sect1>
+  <sect1>
+    <title>Maintaining the patch series</title>
+
+    <para>In my work, I use a number of guards to control which
+      patches are to be applied.</para>
+
+    <itemizedlist>
+      <listitem><para><quote>Accepted</quote> patches are guarded with
+	  <literal>accepted</literal>.  I enable this guard most of
+	  the time.  When I'm applying the patches on top of a tree
+	  where the patches are already present, I can turn this patch
+	  off, and the patches that follow it will apply
+	  cleanly.</para>
+      </listitem>
+      <listitem><para>Patches that are <quote>finished</quote>, but
+	  not yet submitted, have no guards.  If I'm applying the
+	  patch stack to a copy of the upstream tree, I don't need to
+	  enable any guards in order to get a reasonably safe source
+	  tree.</para>
+      </listitem>
+      <listitem><para>Those patches that need reworking before being
+	  resubmitted are guarded with
+	  <literal>rework</literal>.</para>
+      </listitem>
+      <listitem><para>For those patches that are still under
+	  development, I use <literal>devel</literal>.</para>
+      </listitem>
+      <listitem><para>A backport patch may have several guards, one
+	  for each version of the kernel to which it applies.  For
+	  example, a patch that backports a piece of code to 2.6.9
+	  will have a <literal>2.6.9</literal> guard.</para>
+      </listitem></itemizedlist>
+    <para>This variety of guards gives me considerable flexibility in
+      determining what kind of source tree I want to end up with.  For
+      most situations, the selection of appropriate guards is
+      automated during the build process, but I can manually tune the
+      guards to use for less common circumstances.</para>
+
+    <sect2>
+      <title>The art of writing backport patches</title>
+
+      <para>Using MQ, writing a backport patch is a simple process.
+	All such a patch has to do is modify a piece of code that uses
+	a kernel feature not present in the older version of the
+	kernel, so that the driver continues to work correctly under
+	that older version.</para>
+
+      <para>A useful goal when writing a good backport patch is to
+	make your code look as if it was written for the older version
+	of the kernel you're targeting.  The less obtrusive the patch,
+	the easier it will be to understand and maintain.  If you're
+	writing a collection of backport patches to avoid the
+	<quote>rat's nest</quote> effect of lots of
+	<literal>#ifdef</literal>s (hunks of source code that are only
+	used conditionally) in your code, don't introduce
+	version-dependent <literal>#ifdef</literal>s into the patches.
+	Instead, write several patches, each of which makes
+	unconditional changes, and control their application using
+	guards.</para>
+
+      <para>There are two reasons to divide backport patches into a
+	distinct group, away from the <quote>regular</quote> patches
+	whose effects they modify. The first is that intermingling the
+	two makes it more difficult to use a tool like the <literal
+	  role="hg-ext">patchbomb</literal> extension to automate the
+	process of submitting the patches to an upstream maintainer.
+	The second is that a backport patch could perturb the context
+	in which a subsequent regular patch is applied, making it
+	impossible to apply the regular patch cleanly
+	<emphasis>without</emphasis> the earlier backport patch
+	already being applied.</para>
+
+    </sect2>
+  </sect1>
+  <sect1>
+    <title>Useful tips for developing with MQ</title>
+
+    <sect2>
+      <title>Organising patches in directories</title>
+
+      <para>If you're working on a substantial project with MQ, it's
+	not difficult to accumulate a large number of patches.  For
+	example, I have one patch repository that contains over 250
+	patches.</para>
+
+      <para>If you can group these patches into separate logical
+	categories, you can if you like store them in different
+	directories; MQ has no problems with patch names that contain
+	path separators.</para>
+
+    </sect2>
+    <sect2 id="mq-collab:tips:interdiff">
+      <title>Viewing the history of a patch</title>
+
+      <para>If you're developing a set of patches over a long time,
+	it's a good idea to maintain them in a repository, as
+	discussed in section <xref linkend="sec:mq:repo"/>.  If you do
+	so, you'll quickly
+	discover that using the <command role="hg-cmd">hg
+	  diff</command> command to look at the history of changes to
+	a patch is unworkable.  This is in part because you're looking
+	at the second derivative of the real code (a diff of a diff),
+	but also because MQ adds noise to the process by modifying
+	time stamps and directory names when it updates a
+	patch.</para>
+
+      <para>However, you can use the <literal
+	  role="hg-ext">extdiff</literal> extension, which is bundled
+	with Mercurial, to turn a diff of two versions of a patch into
+	something readable.  To do this, you will need a third-party
+	package called <literal role="package">patchutils</literal>
+	<citation>web:patchutils</citation>.  This provides a command
+	named <command>interdiff</command>, which shows the
+	differences between two diffs as a diff.  Used on two versions
+	of the same diff, it generates a diff that represents the diff
+	from the first to the second version.</para>
+
+      <para>You can enable the <literal
+	  role="hg-ext">extdiff</literal> extension in the usual way,
+	by adding a line to the <literal
+	  role="rc-extensions">extensions</literal> section of your
+	<filename role="special"> /.hgrc</filename>.</para>
+      <programlisting>[extensions] extdiff =</programlisting>
+      <para>The <command>interdiff</command> command expects to be
+	passed the names of two files, but the <literal
+	  role="hg-ext">extdiff</literal> extension passes the program
+	it runs a pair of directories, each of which can contain an
+	arbitrary number of files.  We thus need a small program that
+	will run <command>interdiff</command> on each pair of files in
+	these two directories.  This program is available as <filename
+	  role="special">hg-interdiff</filename> in the <filename
+	  class="directory">examples</filename> directory of the
+	source code repository that accompanies this book. <!--
+	&example.hg-interdiff; --></para>
+
+      <para>With the <filename role="special">hg-interdiff</filename>
+	program in your shell's search path, you can run it as
+	follows, from inside an MQ patch directory:</para>
+      <programlisting>hg extdiff -p hg-interdiff -r A:B
+	my-change.patch</programlisting>
+      <para>Since you'll probably want to use this long-winded command
+	a lot, you can get <literal role="hg-ext">hgext</literal> to
+	make it available as a normal Mercurial command, again by
+	editing your <filename role="special">
+	  /.hgrc</filename>.</para>
+      <programlisting>[extdiff] cmd.interdiff =
+	hg-interdiff</programlisting>
+      <para>This directs <literal role="hg-ext">hgext</literal> to
+	make an <literal>interdiff</literal> command available, so you
+	can now shorten the previous invocation of <command
+	  role="hg-ext-extdiff">extdiff</command> to something a
+	little more wieldy.</para>
+      <programlisting>hg interdiff -r A:B
+	my-change.patch</programlisting>
+
+      <note>
+	<para>  The <command>interdiff</command> command works well
+	  only if the underlying files against which versions of a
+	  patch are generated remain the same.  If you create a patch,
+	  modify the underlying files, and then regenerate the patch,
+	  <command>interdiff</command> may not produce useful
+	  output.</para>
+      </note>
+
+      <para>The <literal role="hg-ext">extdiff</literal> extension is
+	useful for more than merely improving the presentation of MQ
+	patches.  To read more about it, go to section <xref
+	  linkend="sec:hgext:extdiff"/>.</para>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 en/ch14-hgext.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/en/ch14-hgext.xml	Wed Feb 18 00:22:09 2009 -0800
@@ -0,0 +1,549 @@
+<!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
+
+<chapter id="chap:hgext">
+  <title>Adding functionality with extensions</title>
+
+  <para>While the core of Mercurial is quite complete from a
+    functionality standpoint, it's deliberately shorn of fancy
+    features.  This approach of preserving simplicity keeps the
+    software easy to deal with for both maintainers and users.</para>
+
+  <para>However, Mercurial doesn't box you in with an inflexible
+    command set: you can add features to it as
+    <emphasis>extensions</emphasis> (sometimes known as
+    <emphasis>plugins</emphasis>).  We've already discussed a few of
+    these extensions in earlier chapters.</para>
+  <itemizedlist>
+    <listitem><para>Section <xref linkend="sec:tour-merge:fetch"/>
+	covers the <literal role="hg-ext">fetch</literal> extension;
+	this combines pulling new changes and merging them with local
+	changes into a single command, <command
+	  role="hg-ext-fetch">fetch</command>.</para>
+    </listitem>
+    <listitem><para>In chapter <xref linkend="chap:hook"/>, we covered
+	several extensions that are useful for hook-related
+	functionality: <literal role="hg-ext">acl</literal> adds
+	access control lists; <literal
+	  role="hg-ext">bugzilla</literal> adds integration with the
+	Bugzilla bug tracking system; and <literal
+	  role="hg-ext">notify</literal> sends notification emails on
+	new changes.</para>
+    </listitem>
+    <listitem><para>The Mercurial Queues patch management extension is
+	so invaluable that it merits two chapters and an appendix all
+	to itself. Chapter <xref linkend="chap:mq"/> covers the
+	basics; chapter <xref
+	  linkend="chap:mq-collab"/> discusses advanced topics;
+	and appendix <xref linkend="chap:mqref"/> goes into detail on
+	each
+	command.</para>
+    </listitem></itemizedlist>
+
+  <para>In this chapter, we'll cover some of the other extensions that
+    are available for Mercurial, and briefly touch on some of the
+    machinery you'll need to know about if you want to write an
+    extension of your own.</para>
+  <itemizedlist>
+    <listitem><para>In section <xref linkend="sec:hgext:inotify"/>,
+	we'll discuss the possibility of <emphasis>huge</emphasis>
+	performance improvements using the <literal
+	  role="hg-ext">inotify</literal> extension.</para>
+    </listitem></itemizedlist>
+
+  <sect1 id="sec:hgext:inotify">
+    <title>Improve performance with the <literal
+	role="hg-ext">inotify</literal> extension</title>
+
+    <para>Are you interested in having some of the most common
+      Mercurial operations run as much as a hundred times faster?
+      Read on!</para>
+
+    <para>Mercurial has great performance under normal circumstances.
+      For example, when you run the <command role="hg-cmd">hg
+	status</command> command, Mercurial has to scan almost every
+      directory and file in your repository so that it can display
+      file status.  Many other Mercurial commands need to do the same
+      work behind the scenes; for example, the <command
+	role="hg-cmd">hg diff</command> command uses the status
+      machinery to avoid doing an expensive comparison operation on
+      files that obviously haven't changed.</para>
+
+    <para>Because obtaining file status is crucial to good
+      performance, the authors of Mercurial have optimised this code
+      to within an inch of its life.  However, there's no avoiding the
+      fact that when you run <command role="hg-cmd">hg
+	status</command>, Mercurial is going to have to perform at
+      least one expensive system call for each managed file to
+      determine whether it's changed since the last time Mercurial
+      checked.  For a sufficiently large repository, this can take a
+      long time.</para>
+
+    <para>To put a number on the magnitude of this effect, I created a
+      repository containing 150,000 managed files.  I timed <command
+	role="hg-cmd">hg status</command> as taking ten seconds to
+      run, even when <emphasis>none</emphasis> of those files had been
+      modified.</para>
+
+    <para>Many modern operating systems contain a file notification
+      facility. If a program signs up to an appropriate service, the
+      operating system will notify it every time a file of interest is
+      created, modified, or deleted.  On Linux systems, the kernel
+      component that does this is called
+      <literal>inotify</literal>.</para>
+
+    <para>Mercurial's <literal role="hg-ext">inotify</literal>
+      extension talks to the kernel's <literal>inotify</literal>
+      component to optimise <command role="hg-cmd">hg status</command>
+      commands.  The extension has two components.  A daemon sits in
+      the background and receives notifications from the
+      <literal>inotify</literal> subsystem.  It also listens for
+      connections from a regular Mercurial command.  The extension
+      modifies Mercurial's behaviour so that instead of scanning the
+      filesystem, it queries the daemon.  Since the daemon has perfect
+      information about the state of the repository, it can respond
+      with a result instantaneously, avoiding the need to scan every
+      directory and file in the repository.</para>
+
+    <para>Recall the ten seconds that I measured plain Mercurial as
+      taking to run <command role="hg-cmd">hg status</command> on a
+      150,000 file repository.  With the <literal
+	role="hg-ext">inotify</literal> extension enabled, the time
+      dropped to 0.1 seconds, a factor of <emphasis>one
+	hundred</emphasis> faster.</para>
+
+    <para>Before we continue, please pay attention to some
+      caveats.</para>
+    <itemizedlist>
+      <listitem><para>The <literal role="hg-ext">inotify</literal>
+	  extension is Linux-specific.  Because it interfaces directly
+	  to the Linux kernel's <literal>inotify</literal> subsystem,
+	  it does not work on other operating systems.</para>
+      </listitem>
+      <listitem><para>It should work on any Linux distribution that
+	  was released after early 2005.  Older distributions are
+	  likely to have a kernel that lacks
+	  <literal>inotify</literal>, or a version of
+	  <literal>glibc</literal> that does not have the necessary
+	  interfacing support.</para>
+      </listitem>
+      <listitem><para>Not all filesystems are suitable for use with
+	  the <literal role="hg-ext">inotify</literal> extension.
+	  Network filesystems such as NFS are a non-starter, for
+	  example, particularly if you're running Mercurial on several
+	  systems, all mounting the same network filesystem.  The
+	  kernel's <literal>inotify</literal> system has no way of
+	  knowing about changes made on another system.  Most local
+	  filesystems (e.g. ext3, XFS, ReiserFS) should work
+	  fine.</para>
+      </listitem></itemizedlist>
+
+    <para>The <literal role="hg-ext">inotify</literal> extension is
+      not yet shipped with Mercurial as of May 2007, so it's a little
+      more involved to set up than other extensions.  But the
+      performance improvement is worth it!</para>
+
+    <para>The extension currently comes in two parts: a set of patches
+      to the Mercurial source code, and a library of Python bindings
+      to the <literal>inotify</literal> subsystem.</para>
+    <note>
+      <para>  There are <emphasis>two</emphasis> Python
+	<literal>inotify</literal> binding libraries.  One of them is
+	called <literal>pyinotify</literal>, and is packaged by some
+	Linux distributions as <literal>python-inotify</literal>.
+	This is <emphasis>not</emphasis> the one you'll need, as it is
+	too buggy and inefficient to be practical.</para>
+    </note>
+    <para>To get going, it's best to already have a functioning copy
+      of Mercurial installed.</para>
+    <note>
+      <para>  If you follow the instructions below, you'll be
+	<emphasis>replacing</emphasis> and overwriting any existing
+	installation of Mercurial that you might already have, using
+	the latest <quote>bleeding edge</quote> Mercurial code. Don't
+	say you weren't warned!</para>
+    </note>
+    <orderedlist>
+      <listitem><para>Clone the Python <literal>inotify</literal>
+	  binding repository.  Build and install it.</para>
+	<programlisting>
+	  hg clone http://hg.kublai.com/python/inotify cd inotify
+	  python setup.py build --force sudo python setup.py install
+	  --skip-build
+	</programlisting>
+      </listitem>
+      <listitem><para>Clone the <filename
+	    class="directory">crew</filename> Mercurial repository.
+	  Clone the <literal role="hg-ext">inotify</literal> patch
+	  repository so that Mercurial Queues will be able to apply
+	  patches to your cope of the <filename
+	    class="directory">crew</filename> repository.</para>
+	<programlisting>
+	  hg clone http://hg.intevation.org/mercurial/crew hg clone
+	  crew inotify hg clone
+	  http://hg.kublai.com/mercurial/patches/inotify
+	  inotify/.hg/patches
+	</programlisting>
+      </listitem>
+      <listitem><para>Make sure that you have the Mercurial Queues
+	  extension, <literal role="hg-ext">mq</literal>, enabled.  If
+	  you've never used MQ, read section <xref
+	    linkend="sec:mq:start"/> to get started
+	  quickly.</para>
+      </listitem>
+      <listitem><para>Go into the <filename
+	    class="directory">inotify</filename> repo, and apply all
+	  of the <literal role="hg-ext">inotify</literal> patches
+	  using the <option role="hg-ext-mq-cmd-qpush-opt">hg
+	    -a</option> option to the <command
+	    role="hg-ext-mq">qpush</command> command.</para>
+	<programlisting>
+	  cd inotify hg qpush -a
+	</programlisting>
+      </listitem>
+      <listitem><para>  If you get an error message from <command
+	    role="hg-ext-mq">qpush</command>, you should not continue.
+	  Instead, ask for help.</para>
+      </listitem>
+      <listitem><para>Build and install the patched version of
+	  Mercurial.</para>
+	<programlisting>
+	  python setup.py build --force sudo python setup.py install
+	  --skip-build
+	</programlisting>
+      </listitem>
+    </orderedlist>
+    <para>Once you've build a suitably patched version of Mercurial,
+      all you need to do to enable the <literal
+	role="hg-ext">inotify</literal> extension is add an entry to
+      your <filename role="special"> /.hgrc</filename>.</para>
+    <programlisting>[extensions] inotify =</programlisting>
+    <para>When the <literal role="hg-ext">inotify</literal> extension
+      is enabled, Mercurial will automatically and transparently start
+      the status daemon the first time you run a command that needs
+      status in a repository.  It runs one status daemon per
+      repository.</para>
+
+    <para>The status daemon is started silently, and runs in the
+      background.  If you look at a list of running processes after
+      you've enabled the <literal role="hg-ext">inotify</literal>
+      extension and run a few commands in different repositories,
+      you'll thus see a few <literal>hg</literal> processes sitting
+      around, waiting for updates from the kernel and queries from
+      Mercurial.</para>
+
+    <para>The first time you run a Mercurial command in a repository
+      when you have the <literal role="hg-ext">inotify</literal>
+      extension enabled, it will run with about the same performance
+      as a normal Mercurial command.  This is because the status
+      daemon needs to perform a normal status scan so that it has a
+      baseline against which to apply later updates from the kernel.
+      However, <emphasis>every</emphasis> subsequent command that does
+      any kind of status check should be noticeably faster on
+      repositories of even fairly modest size.  Better yet, the bigger
+      your repository is, the greater a performance advantage you'll
+      see.  The <literal role="hg-ext">inotify</literal> daemon makes
+      status operations almost instantaneous on repositories of all
+      sizes!</para>
+
+    <para>If you like, you can manually start a status daemon using
+      the <command role="hg-ext-inotify">inserve</command> command.
+      This gives you slightly finer control over how the daemon ought
+      to run.  This command will of course only be available when the
+      <literal role="hg-ext">inotify</literal> extension is
+      enabled.</para>
+
+    <para>When you're using the <literal
+	role="hg-ext">inotify</literal> extension, you should notice
+      <emphasis>no difference at all</emphasis> in Mercurial's
+      behaviour, with the sole exception of status-related commands
+      running a whole lot faster than they used to.  You should
+      specifically expect that commands will not print different
+      output; neither should they give different results. If either of
+      these situations occurs, please report a bug.</para>
+
+  </sect1>
+  <sect1 id="sec:hgext:extdiff">
+    <title>Flexible diff support with the <literal
+	role="hg-ext">extdiff</literal> extension</title>
+
+    <para>Mercurial's built-in <command role="hg-cmd">hg
+	diff</command> command outputs plaintext unified diffs. <!--
+      &interaction.extdiff.diff; --> If you would like to use an
+      external tool to display modifications, you'll want to use the
+      <literal role="hg-ext">extdiff</literal> extension.  This will
+      let you use, for example, a graphical diff tool.</para>
+
+    <para>The <literal role="hg-ext">extdiff</literal> extension is
+      bundled with Mercurial, so it's easy to set up.  In the <literal
+	role="rc-extensions">extensions</literal> section of your
+      <filename role="special"> /.hgrc</filename>, simply add a
+      one-line entry to enable the extension.</para>
+    <programlisting>[extensions] extdiff =</programlisting>
+    <para>This introduces a command named <command
+	role="hg-ext-extdiff">extdiff</command>, which by default uses
+      your system's <command>diff</command> command to generate a
+      unified diff in the same form as the built-in <command
+	role="hg-cmd">hg diff</command> command. <!--
+      &interaction.extdiff.extdiff; --> The result won't be exactly
+      the same as with the built-in <command role="hg-cmd">hg
+	diff</command> variations, because the output of
+      <command>diff</command> varies from one system to another, even
+      when passed the same options.</para>
+
+    <para>As the <quote><literal>making snapshot</literal></quote>
+      lines of output above imply, the <command
+	role="hg-ext-extdiff">extdiff</command> command works by
+      creating two snapshots of your source tree.  The first snapshot
+      is of the source revision; the second, of the target revision or
+      working directory.  The <command
+	role="hg-ext-extdiff">extdiff</command> command generates
+      these snapshots in a temporary directory, passes the name of
+      each directory to an external diff viewer, then deletes the
+      temporary directory.  For efficiency, it only snapshots the
+      directories and files that have changed between the two
+      revisions.</para>
+
+    <para>Snapshot directory names have the same base name as your
+      repository. If your repository path is <filename
+	class="directory">/quux/bar/foo</filename>, then <filename
+	class="directory">foo</filename> will be the name of each
+      snapshot directory.  Each snapshot directory name has its
+      changeset ID appended, if appropriate.  If a snapshot is of
+      revision <literal>a631aca1083f</literal>, the directory will be
+      named <filename class="directory">foo.a631aca1083f</filename>.
+      A snapshot of the working directory won't have a changeset ID
+      appended, so it would just be <filename
+	class="directory">foo</filename> in this example.  To see what
+      this looks like in practice, look again at the <command
+	role="hg-ext-extdiff">extdiff</command> example above.  Notice
+      that the diff has the snapshot directory names embedded in its
+      header.</para>
+
+    <para>The <command role="hg-ext-extdiff">extdiff</command> command
+      accepts two important options. The <option
+	role="hg-ext-extdiff-cmd-extdiff-opt">hg -p</option> option
+      lets you choose a program to view differences with, instead of
+      <command>diff</command>.  With the <option
+	role="hg-ext-extdiff-cmd-extdiff-opt">hg -o</option> option,
+      you can change the options that <command
+	role="hg-ext-extdiff">extdiff</command> passes to the program
+      (by default, these options are
+      <quote><literal>-Npru</literal></quote>, which only make sense
+      if you're running <command>diff</command>).  In other respects,
+      the <command role="hg-ext-extdiff">extdiff</command> command
+      acts similarly to the built-in <command role="hg-cmd">hg
+	diff</command> command: you use the same option names, syntax,
+      and arguments to specify the revisions you want, the files you
+      want, and so on.</para>
+
+    <para>As an example, here's how to run the normal system
+      <command>diff</command> command, getting it to generate context
+      diffs (using the <option role="cmd-opt-diff">-c</option> option)
+      instead of unified diffs, and five lines of context instead of
+      the default three (passing <literal>5</literal> as the argument
+      to the <option role="cmd-opt-diff">-C</option> option). <!--
+      &interaction.extdiff.extdiff-ctx; --></para>
+
+    <para>Launching a visual diff tool is just as easy.  Here's how to
+      launch the <command>kdiff3</command> viewer.</para>
+    <programlisting>hg extdiff -p kdiff3 -o</programlisting>
+
+    <para>If your diff viewing command can't deal with directories,
+      you can easily work around this with a little scripting.  For an
+      example of such scripting in action with the <literal
+	role="hg-ext">mq</literal> extension and the
+      <command>interdiff</command> command, see section <xref
+	linkend="mq-collab:tips:interdiff"/>.</para>
+
+    <sect2>
+      <title>Defining command aliases</title>
+
+      <para>It can be cumbersome to remember the options to both the
+	<command role="hg-ext-extdiff">extdiff</command> command and
+	the diff viewer you want to use, so the <literal
+	  role="hg-ext">extdiff</literal> extension lets you define
+	<emphasis>new</emphasis> commands that will invoke your diff
+	viewer with exactly the right options.</para>
+
+      <para>All you need to do is edit your <filename role="special">
+	  /.hgrc</filename>, and add a section named <literal
+	  role="rc-extdiff">extdiff</literal>.  Inside this section,
+	you can define multiple commands.  Here's how to add a
+	<literal>kdiff3</literal> command.  Once you've defined this,
+	you can type <quote><literal>hg kdiff3</literal></quote> and
+	the <literal role="hg-ext">extdiff</literal> extension will
+	run <command>kdiff3</command> for you.</para>
+      <programlisting>[extdiff] cmd.kdiff3 =</programlisting>
+      <para>If you leave the right hand side of the definition empty,
+	as above, the <literal role="hg-ext">extdiff</literal>
+	extension uses the name of the command you defined as the name
+	of the external program to run.  But these names don't have to
+	be the same.  Here, we define a command named
+	<quote><literal>hg wibble</literal></quote>, which runs
+	<command>kdiff3</command>.</para>
+      <programlisting>[extdiff] cmd.wibble = kdiff3</programlisting>
+
+      <para>You can also specify the default options that you want to
+	invoke your diff viewing program with.  The prefix to use is
+	<quote><literal>opts.</literal></quote>, followed by the name
+	of the command to which the options apply.  This example
+	defines a <quote><literal>hg vimdiff</literal></quote> command
+	that runs the <command>vim</command> editor's
+	<literal>DirDiff</literal> extension.</para>
+      <programlisting>[extdiff] cmd.vimdiff = vim opts.vimdiff = -f
+	'+next' '+execute "DirDiff" argv(0) argv(1)'</programlisting>
+
+    </sect2>
+  </sect1>
+  <sect1 id="sec:hgext:transplant">
+    <title>Cherrypicking changes with the <literal
+	role="hg-ext">transplant</literal> extension</title>
+
+    <para>Need to have a long chat with Brendan about this.</para>
+
+  </sect1>
+  <sect1 id="sec:hgext:patchbomb">
+    <title>Send changes via email with the <literal
+	role="hg-ext">patchbomb</literal> extension</title>
+
+    <para>Many projects have a culture of <quote>change
+	review</quote>, in which people send their modifications to a
+      mailing list for others to read and comment on before they
+      commit the final version to a shared repository.  Some projects
+      have people who act as gatekeepers; they apply changes from
+      other people to a repository to which those others don't have
+      access.</para>
+
+    <para>Mercurial makes it easy to send changes over email for
+      review or application, via its <literal
+	role="hg-ext">patchbomb</literal> extension.  The extension is
+      so namd because changes are formatted as patches, and it's usual
+      to send one changeset per email message.  Sending a long series
+      of changes by email is thus much like <quote>bombing</quote> the
+      recipient's inbox, hence <quote>patchbomb</quote>.</para>
+
+    <para>As usual, the basic configuration of the <literal
+	role="hg-ext">patchbomb</literal> extension takes just one or
+      two lines in your <filename role="special">
+	/.hgrc</filename>.</para>
+    <programlisting>[extensions] patchbomb =</programlisting>
+    <para>Once you've enabled the extension, you will have a new
+      command available, named <command
+	role="hg-ext-patchbomb">email</command>.</para>
+
+    <para>The safest and best way to invoke the <command
+	role="hg-ext-patchbomb">email</command> command is to
+      <emphasis>always</emphasis> run it first with the <option
+	role="hg-ext-patchbomb-cmd-email-opt">hg -n</option> option.
+      This will show you what the command <emphasis>would</emphasis>
+      send, without actually sending anything.  Once you've had a
+      quick glance over the changes and verified that you are sending
+      the right ones, you can rerun the same command, with the <option
+	role="hg-ext-patchbomb-cmd-email-opt">hg -n</option> option
+      removed.</para>
+
+    <para>The <command role="hg-ext-patchbomb">email</command> command
+      accepts the same kind of revision syntax as every other
+      Mercurial command.  For example, this command will send every
+      revision between 7 and <literal>tip</literal>, inclusive.</para>
+    <programlisting>hg email -n 7:tip</programlisting>
+    <para>You can also specify a <emphasis>repository</emphasis> to
+      compare with.  If you provide a repository but no revisions, the
+      <command role="hg-ext-patchbomb">email</command> command will
+      send all revisions in the local repository that are not present
+      in the remote repository.  If you additionally specify revisions
+      or a branch name (the latter using the <option
+	role="hg-ext-patchbomb-cmd-email-opt">hg -b</option> option),
+      this will constrain the revisions sent.</para>
+
+    <para>It's perfectly safe to run the <command
+	role="hg-ext-patchbomb">email</command> command without the
+      names of the people you want to send to: if you do this, it will
+      just prompt you for those values interactively.  (If you're
+      using a Linux or Unix-like system, you should have enhanced
+      <literal>readline</literal>-style editing capabilities when
+      entering those headers, too, which is useful.)</para>
+
+    <para>When you are sending just one revision, the <command
+	role="hg-ext-patchbomb">email</command> command will by
+      default use the first line of the changeset description as the
+      subject of the single email message it sends.</para>
+
+    <para>If you send multiple revisions, the <command
+	role="hg-ext-patchbomb">email</command> command will usually
+      send one message per changeset.  It will preface the series with
+      an introductory message, in which you should describe the
+      purpose of the series of changes you're sending.</para>
+
+    <sect2>
+      <title>Changing the behaviour of patchbombs</title>
+
+      <para>Not every project has exactly the same conventions for
+	sending changes in email; the <literal
+	  role="hg-ext">patchbomb</literal> extension tries to
+	accommodate a number of variations through command line
+	options.</para>
+      <itemizedlist>
+	<listitem><para>You can write a subject for the introductory
+	    message on the command line using the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg -s</option>
+	    option.  This takes one argument, the text of the subject
+	    to use.</para>
+	</listitem>
+	<listitem><para>To change the email address from which the
+	    messages originate, use the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg -f</option>
+	    option.  This takes one argument, the email address to
+	    use.</para>
+	</listitem>
+	<listitem><para>The default behaviour is to send unified diffs
+	    (see section <xref linkend="sec:mq:patch"/> for a
+	    description of the
+	    format), one per message.  You can send a binary bundle
+	    instead with the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg -b</option>
+	    option.</para>
+	</listitem>
+	<listitem><para>Unified diffs are normally prefaced with a
+	    metadata header.  You can omit this, and send unadorned
+	    diffs, with the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg
+	      --plain</option> option.</para>
+	</listitem>
+	<listitem><para>Diffs are normally sent <quote>inline</quote>,
+	    in the same body part as the description of a patch.  This
+	    makes it easiest for the largest number of readers to
+	    quote and respond to parts of a diff, as some mail clients
+	    will only quote the first MIME body part in a message. If
+	    you'd prefer to send the description and the diff in
+	    separate body parts, use the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg -a</option>
+	    option.</para>
+	</listitem>
+	<listitem><para>Instead of sending mail messages, you can
+	    write them to an <literal>mbox</literal>-format mail
+	    folder using the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg -m</option>
+	    option.  That option takes one argument, the name of the
+	    file to write to.</para>
+	</listitem>
+	<listitem><para>If you would like to add a
+	    <command>diffstat</command>-format summary to each patch,
+	    and one to the introductory message, use the <option
+	      role="hg-ext-patchbomb-cmd-email-opt">hg -d</option>
+	    option.  The <command>diffstat</command> command displays
+	    a table containing the name of each file patched, the
+	    number of lines affected, and a histogram showing how much
+	    each file is modified.  This gives readers a qualitative
+	    glance at how complex a patch is.</para>
+	</listitem></itemizedlist>
+
+    </sect2>
+  </sect1>
+</chapter>
+
+<!--
+local variables: 
+sgml-parent-document: ("00book.xml" "book" "chapter")
+end:
+-->
diff -r 8631da51309b -r b90b024729f1 tools/latex-to-docbook
--- a/tools/latex-to-docbook	Mon Feb 09 23:25:40 2009 -0800
+++ b/tools/latex-to-docbook	Wed Feb 18 00:22:09 2009 -0800
@@ -33,7 +33,7 @@
         line = (line.rstrip()
                 .replace('~', ' ')
                 .replace('&', '&amp;')
-                .replace('&emdash;', '&emdash;')
+                .replace('---', '&emdash;')
                 .replace('\_', '_')
                 .replace('\{', '{')
                 .replace('\}', '}')
@@ -83,7 +83,7 @@
         line = re.sub(r'\\filename{(?P<file>[^}]+?)}',
                       r'<filename>\g<file></filename>', line)
         line = re.sub(r'\\tildefile{(?P<file>[^}]+)}',
-                      r'<filename role="home"> /\g<file></filename>', line)
+                      r'<filename role="home">~/\g<file></filename>', line)
         line = re.sub(r'\\sfilename{(?P<file>[^}]+)}',
                       r'<filename role="special">\g<file></filename>', line)
         line = re.sub(r'\\sdirname{(?P<dir>[^}]+)}',
@@ -95,7 +95,7 @@
         line = re.sub(r'\\pymod{(?P<mod>[^}]+)}',
                       r'<literal role="py-mod">\g<mod></literal>', line)
         line = re.sub(r'\\pymodclass{(?P<mod>[^}]+)}{(?P<class>[^}]+)}',
-                      r'<literal url="py-mod-\g<mod>">\g<class></ulink>', line)
+                      r'<literal role="py-mod-\g<mod>">\g<class></literal>', line)
         line = re.sub(r'\\url{(?P<url>[^}]+)}',
                       r'<ulink url="\g<url>">\g<url></ulink>', line)
         line = re.sub(r'\\href{(?P<url>[^}]+)}{(?P<text>[^}]+)}',
@@ -154,7 +154,7 @@
                         inlist = 1
                 else:
                     ofp.write('</')
-                    if env == ('itemizedlist', 'orderedlist'):
+                    if env in ('itemizedlist', 'orderedlist'):
                         inlist = 0
                 print >> ofp, env + '>'
             else: